Cellulosic article containing an olefinic oxide polymer and method of manufacture

ABSTRACT

A tubular cellulosic casing comprising cellulose or a cellulose derivative which has incorporated therewith a polyethylene oxide composition having a molecular weight of at least 70,000 and a method of manufacturing the same.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part application ofcopending U.S. application Ser. No. 07/846,455 filed Mar. 4, 1992 whichis now abandoned, which application is hereby incorporated by referencein its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a cellulosic article and a method formanufacturing same. The present invention is particularly suitable fortubular food casings, such as sausage casings which may be provided in ashirred form.

It is known that cellulosic articles may be made by a variety ofprocedures. For example, cellulose with or without chemicalmodifications, may be put into solution with a solvent, e.g. bydispersion or by dissolution, and then shaped into an article followedby solvent removal (with or without chemical modification of thecellulose) to solidify or set the shape of the formed cellulosicarticle. Examples of known processes for production of cellulosicarticles are the viscose, cuprammonium, N-methyl-morpholine-n-oxide,zinc chloride and cellulose carbamate processes as described e.g. inU.S. Pat. Nos. 1,601,686; 2,651,582; 4,145,532; 4,426,228; 4,781,931;4,789,006; 4,867,204; and 4,999,149, the teachings of which are allhereby incorporated by reference. The formed article may have a varietyof shapes including a filament, bead, sheet or film. It is contemplatedthat the present invention may utilize any known method of producing acellulosic article of any shape. With further respect to the presentinvention, although the article may be of any shape, preferred arefilms, generally having a thickness of 10 mils (254 microns) or less.Both planar, spherical, cylindrical and tubular articles arecontemplated with seamless tubular articles being preferred and tubularfilms being especially preferred.

The present invention is particularly useful with respect to themanufacture and use of food casings. Food casings used in the processedfood industry are generally thin-walled tubing of various diametersprepared from regenerated cellulose, cellulose derivatives, and thelike.

In general, cellulosic food casings have multifunctional uses in thatthey may be employed as molding containers during the processing of thefood product encased therein and also serve as a protective wrapping forthe finished product. In the sausage meat industry, the preparation ofvarious types of sausages such as frankfurters in a variety of sizesusually involves removing the casing from about the processed meat priorto final packaging. These sausages from which casing is usually removedare generally formed and processed in nonfiber-reinforced (nonfibrous)cellulose casing. However, larger diameter sausages such as salami arefrequently sold with the casing left on. These sausages are usuallyformed and processed in fiber-reinforced (fibrous) cellulosic casing.

The starting material in the manufacture of cellulosic food casings ishigh quality, relatively pure cellulose pulp (either cotton or wood),most typically in sheet form. In present commercial manufacture ofnonfibrous cellulose sausage casings, regenerated cellulose is generallymade using the well known viscose process whereby viscose is typicallyextruded through an annular die into a coagulating and regenerating bathto produce a tube of regenerated cellulose. (Rayon filaments or threadsmay be similarly made by extrusion through a spinning nozzle accordingto well known methods.) This tube is subsequently washed, plasticizede.g. with glycerine, and dried e.g. by inflation under substantial airpressure. A typical commercial viscose process is described below whichutilizes cellulosic sheet starting materials having a suitable densitybetween about 0.8-0.9 gm/cc.

This relatively pure cellulose is typically converted to alkalicellulose by steeping in a sodium hydroxide solution. Cellulose absorbsthe sodium hydroxide and the fibers swell and open. The degree ofsteeping is preferably held to the minimum amount necessary to ensureuniform distribution of the sodium hydroxide on the cellulose. Asteeping bath temperature of about 19°-30° C. is preferred, and asuitable sodium hydroxide concentration in the steeping bath is about17-20 wt. %.

In a typical steeping apparatus there is no forced circulation ofcaustic between the cellulose sheets, so it is important that the rateof filling the apparatus with caustic (fill rate) be such that thecaustic reaches every portion of the sheets. The cellulose sheets aretypically held in place in the steeping chamber by a support frame, anda typical steep time in commercial practice is 50-60 minutes.

After steeping, the caustic is drained and excess absorbed sodiumhydroxide solution is pressed out, typically by a hydraulic ram. Atypical alkali cellulose composition is about 13-18% caustic, 30-35%cellulose and the remainder water (by wt.). The percent caustic andcellulose in the alkali cellulose is controlled by the well-known pressweight ratio. This ratio is the weight of the wet cake after pressingdivided by the weight of the original cellulose used. A typical pressratio is about 2.6-3.2. After the press out, the alkali cellulose isshredded, i.e. the fibers in the sheet are pulled apart so that duringxanthation the carbon disulphide contacts all portions of the alkalicellulose. There is an optimum shredding time for each system which canonly be determined by testing. Typical shredding time is about 40-90minutes. Heat is generated during the shredding step and the temperaturemay, for example, be controlled by means of a cooling water jacketaround the shredder, preferably in the range of 25°-35° C.

During a succeeding, preferred aging step, an oxidative process isinitiated which breaks the cellulose molecular chains thereby reducingthe average degree of polymerization which will in turn reduce theviscosity of the viscose to be produced. During the aging step theshredded alkali cellulose is preferably maintained in covered vessels toprevent drying.

The conversion of alkali cellulose to cellulose xanthate is accomplishedby placing the shredded and aged alkali cellulose in a closed reactorknown as a baratte and adding carbon disulphide which vaporizes andreacts with the alkali cellulose to form cellulose xanthate. The amountof carbon disulphide used to achieve the desired conversion to cellulosexanthate is typically equal in weight to about 26-38% of the bone dryweight cellulose in the alkali cellulose, and preferably only enough toproduce cellulose xanthate with acceptable filtration characteristics.

The length of time required for the xanthation reaction (conversion ofalkali cellulose to cellulose xanthate) depends on the reactiontemperature and the quantity of the carbon disulphide. Variations insuch parameters as the quantity of carbon disulphide used as well as thetemperature, and pressure during xanthation is determined by the desireddegree of xanthation. The percent total sulphur is directly related tothe amount of carbon disulphide introduced, including xanthate andby-product sulphur. In general, xanthation reaction conditions arevaried to ensure that adequate conversion is achieved by reaching atotal sulphur content greater than about 1.1 wt. %. Typically, there isabout 0.4-1.5% by wt. sulphur in the by-products admixed with cellulosexanthate.

The purpose of converting alkali cellulose to cellulose xanthate is toenable dissolution of the cellulose in a dilute solution of sodiumhydroxide, e.g. 3.6-5.0 wt. %. This is the so-called viscose formationor "vissolving" step, in which sodium hydroxide is absorbed onto thecellulose xanthate molecule which becomes highly swollen and dissolvesover a finite time period. This step is preferably accelerated bycooling and agitation. Sufficient cooling is preferably provided tomaintain the mixture at about 10° C. or less. The quality of thesolution is typically determined by measuring the filterability of theviscose e.g. by rate of clogging or throughput through a filter such asa cloth filter. The viscose is allowed to ripen and deaerate, isfiltered under controlled temperature and vacuum. During ripening,reactions occur which result in a more uniform distribution of thexanthate group on the cellulose and a gradual decomposition of thexanthate molecule which progressively reduces its ability to remaindissolved, and increases the ease of viscose-cellulose regeneration.

Viscose is essentially a solution of cellulose xanthate in an aqueoussolution of sodium hydroxide. Viscose is aged (by controlling time andtemperature) to promote a more uniformed distribution of xanthate groupsacross the cellulose chains. This aging (also termed "ripening") iscontrolled to facilitate gelation or coagulation. If the desired productis a tube, the tubular form is obtained by forcing the viscose through arestricted opening, for example, an annular gap. The diameter and gapwidth of the opening, as well as the rate at which the viscose is pumpedthrough, are designed in a manner well known to those skilled in the artfor both non-reinforced and fiber-reinforced products such that atubular film casing of specific wall thickness and diameter is formedfrom the viscose.

The extruded viscose casing is converted (coagulated and regenerated) tocellulose in the extrusion bath by action of a mixture of acid and salt,for example, sulphuric acid and sodium sulphate. A typical bath containsabout 7-18% sulfuric acid by weight, and the bath temperature may beabout 30°-56° C.

The cellulose casing emerging from the acid/salt bath is preferablypassed through several dilute acid baths. The purpose of these baths isto ensure completion of the regeneration. During regeneration, gases(such as H₂ S and CS₂) are released through both the inner and outersurfaces of the casing, and means must be provided for removing thesegases from the casing. After the casing has been thoroughly regeneratedand the salt removed, it is preferably passed through a series of heatedwater baths to wash out residual sulfur by-products.

Cellulose articles for use as sausage casing require plasticization e.g.with moisture and/or polyols such as glycerine. Without suchplasticization the casings are too brittle for commercial use.Typically, a softener such as glycerine is added in the final water bathby way of a dip tub, and in a quantity of about 11-16% based on the bonedry cellulose weight (for typical nonfibrous casing). The regeneratedcellulose casings are also typically dried e.g. by inflation with heatedair. After drying, the casing is wound on reels and subsequently shirredon high-speed shirring machines, such as those described in U.S. Pat.Nos. 2,984,574, 3,451,827, 3,454,981, 3,454,982, 3,461,484, 3,988,804and 4,818,551. In the shirring process, lengths of from about 40 toabout 200 feet of casing are typically compacted (shirred) into tubularsticks of between about 4 and about 30 inches. The shirred casing sticksare packaged and provided to the meat processor who typically places thesticks over a stuffing horn and causes the casing sticks to be deshirredat extremely high speeds while stuffing the deshirred casing with afoodstuff such as meat emulsion. The encased foodstuff can besubsequently cooked and the casing removed, from e.g. meat processedtherein, with high-speed peeling machines.

For fibrous casing, a process of manufacture similar to that fornonfibrous casing is employed, however, the viscose is extruded onto oneor both sides of a tube which is usually formed by folding a web ofpaper so that the opposing side edges overlap. In production of fibrouscasing the viscose impregnates the paper tube where it is coagulated andregenerated to produce a fiber-reinforced tube of regenerated cellulose.The paper provides fiber reinforcement which is generally utilized intubular casing having diameters of about 40 mm or more in order toprovide dimensional stability, particularly during stuffing with meatemulsion. Production of both nonfibrous and fibrous casing is well-knownin the art and the present invention may utilize such well knownprocesses modified as disclosed herein.

Cellulosic casings are typically humidified to a level sufficient toallow the casing to be shirred without undue breakage from brittleness.A humectant may be employed to moderate the rate of moisture retentionand casing swelling to produce a casing which during the shirringoperation has sufficient flexibility without undue swelling or stickingof the casing to the shirring mandrel. Typically, a lubricant such as anoil will also be used to facilitate passage of the casing through theshirring equipment e.g. over a shirring mandrel.

It has been useful to lubricate and internally humidify cellulosecasings during the shirring process by spraying a mist of water and alubricant through the shirring mandrel. This is an economical, fast andconvenient way to lubricate and/or humidify the casing to increase theflexibility of the casing and facilitate high speed shirring withoutundue detrimental sticking, tearing or breakage of the casing.

Cellulosic food casings suitable for use in the present invention mayhave a moisture content of less than about 100 wt. % based upon theweight of bone dry cellulose (BDC). The term "bone dry cellulose" asused herein refers to cellulose such as regenerated cellulose and/orpaper which has been dried by heating the cellulose in a convection ovenat 160° C. for one hour to remove water moisture. In the formation ofcellulosic casing e.g. by the viscose process, regenerated celluloseprior to drying forms what is known as gel stock casing having a highmoisture content in excess of 100 wt. % BDC. This gel stock casing isunsuitable for stuffing with food such as meat emulsion, e.g. to formsausages, because it has insufficient strength to maintain control ofstuffing diameter and prevent casing failure due to bursting while undernormal stuffing pressure. Gel stock casing is typically dried to amoisture level well below 100 wt. % (BDC) which causes the regeneratedcellulose to become more dense with increased intermolecular bonding(increased hydrogen bonding). The moisture level of this dried casingmay be adjusted, e.g. by remoisturization, to facilitate stuffing. Suchremoisturization or moisture adjustment to a specific level, fornonfibrous casing, is typically to a level with a range of from about 5to about 40 wt. % BDC. Small diameter nonfibrous casing, prior toshirring, will have been dried to a typical moisture content of about10-20 wt. % BDC, and such small diameter nonfibrous casing when shirredwill have a moisture content that has been adjusted to between about 20to 40 wt. % BDC.

For fibrous casing, casing is commercially produced having a moisturecontent ranging from about 4 wt. % BDC to about 70 wt. % BDC. Typically,fiber-reinforced casing having a moisture level between about 4 to about25 wt. % BDC will be soaked prior to stuffing by a food processor.Premoisturized, ready-to-stuff, fibrous casing is also commercialized.Premoisturized fibrous casing which does not require additional soakingor moisturization will typically have a moisture content of from about26 to about 70 wt. % BDC.

In the formation of skinless (casing removed) frankfurters, sausageproteins coagulate, particularly at the sausage surface, to produce asecondary skin and allow formation of a liquid layer between this formedskin and the casing as described in U.S. Pat. No. 1,631,723 (Freund). Inthe art the term "skinless frankfurter" is understood to mean that thecasing is or is intended to be removed by the producer and that suchcasing may be removed because of formation of the secondary "skin" ofcoagulated proteins on the surface of the frankfurter. This secondaryskin forms the outer surface of the so called "skinless frankfurters".Skin formation is known to be produced by various means including thetraditional smoke curing with gaseous smoke, low temperature drying,application of acids such as citric acid, acetic acid or acidic liquidsmoke or combinations thereof. Desirably, this secondary skin will besmooth and cover the surface of the frankfurter. Formation of a liquidlayer between the casing and the frankfurter skin relates to the meatemulsion formulation, percent relative humidity during the cookingenvironment, subsequent showering and steam application to the chilledfrankfurter and presence of any peeling aid coatings at thecasing/frankfurter interface.

In present commercial production of tubular cellulose casings it wouldbe desirable to improve process efficiency, productivity and costs withrespect to certain process steps. For example, during the celluloseregeneration step, as described above, sulfur-containing gases and watervapor accumulate inside the regenerating tube. These waste gases must beremoved, and this is commonly done by slitting the casing walls atintervals so the waste gases may be vented. However, the slit sectionsof cellulose tube must be ultimately removed and the adjoining sectionsspliced together. This procedure is time consuming, labor intensive andresults in product waste because the slit sections of tubing must bediscarded. So there is a long-standing need in cellulose casingproduction to reduce the required frequency of puncturing/slitting. Thepotential advantages would include higher extrusion speed (if the timeinterval between puncturing/slitting is to remain constant) or longerintervals between puncturing/slitting if the extrusion speed is toremain constant.

One limitation of the prior art cellulose tube manufacturing system isthe time, equipment expense and material cost required to add softenerto the casing. Most commonly this involves the additions of betweenabout 10 and 20% glycerine to nonreinforced cellulose tubing and betweenabout 15 and 35% glycerine to fiber-reinforced cellulosic casing (all ona total weight basis of casing). It is certainly desirable to reduce oreven eliminate the need for this softener addition step. This has notheretofore been possible because low softener content reduces theflexibility of the cellulose tube wall, thereby causing excessivebreakage due to inherent distortions during the shirring and compressionsteps to form the as-sold shirred stick. Low softener content may alsoresult in excessive breakage when, after a storage period of typicallyat least ten weeks before use, the stick is deshirred by the foodprocessor and stuffed with food, e.g. frankfurter emulsion.

Another disadvantage of the softener requirement is that unabsorbedsoftener is a substantially noncompressible liquid which resistscompression during shirring. Moreover, the softener tends to make theshirred and compressed stick expand or grow immediately aftermanufacture, so either the sticks must be allowed time for longitudinalstabilization before packaging for shipment to food processors, orplaced in cartons with unrestricted space at the ends for longitudinalgrowth. The latter is undesirable because the longitudinally slidablesticks may tend to bow and break. It will also be apparent that thesoftener adds weight to the shirred stick shipping carton, and that thecasing manufacturer wishes to provide food processing customers withsticks having the highest useable inflatable casing length per unitlength shirred stick, often referred to as "pack ratio".

Olefinic oxide polymers such as poly(ethylene oxide) are known materialshaving a wide variety of suggested uses. Various grades of acommercially available poly(ethylene oxide) sold under the trademarkPOLYOX® have been suggested as useful as adhesives, flocculants, andfiller retention and drainage aids in the manufacture of paper andpaperboard products. Other suggested uses include, thickeners forpaints, drag-reducing additives for water used in fire fighting,lubricants and thickeners for personal care products such as toothpastesand shaving preparations, and also as dispersant, binders and rheologycontrol agents in a variety of applications. Poly(ethylene oxide) hasalso been used in water soluble packaging films and to increase waterretention in soil. Other functions and uses are disclosed in thebrochure POLYOX® WATER-SOLUBLE RESINS (Union Carbide Chemicals &Plastics Technology Corporation, 1990).

Poly(ethylene oxide) is known as an additive to thermoplastic films topromote biodegradability. It is susceptible to severe auto-oxidativedegradation and loss of viscosity in aqueous solutions. According to theHandbook of Water-Soluble Gums and Resins by Robert C. Davidsons,(published by McGraw-Hill Book Company, 1980) the degradation mechanisminvolves the formation of hydroperoxides that decompose and causecleavage of the polymer chain. The rate of degradation is increased byheat, ultraviolet light, strong acids, or certain transition metal ions.

The present invention ameliorates the above noted limitations ordisadvantages in various embodiments as further described below.

One object of this present invention is to provide an improvedcellulosic tube with lower polyhydric alcohol softener content thanheretofore used.

A further object is to provide a shirred cellulosic tube withoutpolyhydric alcohol softener but still having high coherency and lowbreakage rate.

Another object is to provide a shirred cellulosic tube stick with higherpack efficiency than heretofore achieved under equivalent shirring andcompression conditions.

Still another object is to provide a method for manufacturing acellulosic casing wherein less waste gases are produced during thecellulose regeneration step.

A further object is to provide a sausage casing having improvedpeelability under difficult peeling conditions.

Another object is to provide a casing which either before drying (gelstock) or after drying (semi-finished) has a faster rate of absorptioni.e. it takes up and holds greater amounts of water or liquid based(especially aqueous) coatings such as migrating or nonmigratingcolorants, flavorants, antimycotics, liquid smokes, skin forming agents,preservatives, peeling aids or meat adhesion promoters in a shorterperiod of time.

Still another object is to provide a cellulosic casing having anolefinic oxide polymer such as poly(ethylene oxide) which has an averagemolecular weight of at least about 70,000 uniformly incorporated withcellulose.

An additional object is to provide a cellulosic casing having aplurality of layers or sections wherein an olefinic oxide polymer isuniformly incorporated or dispersed throughout at least one layer orsection (preferably the innermost layer of a tubular article) butoptionally not in all layers or sections.

Yet another object is to provide a casing having a combination of highpacking efficiency and a high bore size.

A further object is to provide a casing having a combination of highpacking efficiency and high pack ratio.

Another object is to provide a method for manufacturing a regeneratedcellulose casing using a viscose process having a faster rate ofregeneration.

Still another object is to provide a method for manufacturing a casingwhich fulfills any of the above objects.

An additional object is to provide a method for manufacturing a shirredcellulosic casing stick with high pack ratio, high coherency and lowbreakage.

These and other objects and advantages of this invention will beapparent from the ensuing disclosure and appended claims. It is notnecessary that each and every object listed above be found in allembodiments of the invention. It is sufficient that the invention may beadvantageously employed relative to the prior art.

SUMMARY OF THE INVENTION

According to the present invention a cellulosic, preferably tubular,article is provided which contains an olefinic oxide polymer, preferablypoly(ethylene oxide), uniformly dispersed in admixture with thecellulose. The olefinic oxide polymer-to-cellulose weight ratio ispreferably at least about 1:200 and the olefinic oxide polymer has anaverage molecular weight of at least about 70,000.

The invention may be suitably employed in the form of nonfibrous orfibrous food casings. The inventive food casing may be stuffed with afood product such as a meat emulsion of e.g. beef, pork, turkey,chicken, fish or mixtures thereof, or with a dairy product such ascheese or with a vegetable product such as soybean-derived protein ortofu. It is contemplated that mixtures of animal and vegetable productsmay be encased and that these products may be cooked or uncooked,pasteurized, fermented, frozen, dried or processed in any of a varietyof well-known ways of processing food. A particular desirable form ofthe invention is an encased meat sausage, and a most advantageous useand embodiment of the invention is for the production of skinlessfrankfurters using small diameter (circumference <115 mm) nonfibrouscasing. Another advantageous embodiment is for the production of largediameter (circumference >115 mm) sausages using fiber-reinforced casingin which the casing is often left on food products if printed, or peeledoff and repackaged if unprinted. An inventive method of manufacture isalso disclosed which admixes the polymer additive in a solution ofcellulose or a cellulose derivative prior to extrusion andsolidification into a formed article.

The invention in its various embodiments exhibits many advantages. It isnot necessary that each embodiment of the invention exhibit or have eachpossible advantage which are disclosed herein. It has been particularlynoted that the present invention may be usefully employed to producecellulosic films particularly from viscose which may have: increasedgloss or transparency, faster by-product removal or wash out; extendedpuncture intervals to remove unwanted gases during the washing steps,faster regeneration and improved moisture control.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of a process for making an articleaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, a tubular cellulosic article such asa casing is provided, which may encase a food product such as a sausage.This inventive casing generally comprises an elongated tube, made of acellulose material, more preferably regenerated cellulose which containsan olefin oxide polymer such as poly(ethylene oxide) incorporatedtherein. Regenerated cellulose may be made by the well known viscoseprocess, however other processes as disclosed above such as thecuprammonium process are known and may be employed.

The casing may advantageously be employed to process food such assausages. The casing may be stuffed with a meat emulsion such as beef,pork or turkey, cooked, and either sold with the casing left on or thecasing may be peeled off and the foodstuff repackaged for retail sale.

Cellulose casings of the present invention may be fiber-reinforced(fibrous) or not (nonfibrous) and may be classified as either smalldiameter casing (circumference less than 115 mm) or large diametercasing (circumference greater than 115 mm). Any size circumference ofnonfibrous casing capable of having utility as a food package issuitable, but preferably the casing will have a circumference of fromabout 1.6 to about 3.8 inches (4.4-9.7 cm). Similarly, for fibrouscasing any circumference will be suitable, but preferably the casingwill have a circumference of from about 4.1 to about 21.6 inches(10.4-54.9 cm).

Generally, the casing wall thickness will be at least 0.7 mil and fornonfibrous casings will range from about 0.7 to about 4 mils (0.02-0.1mm) with larger thicknesses being utilized in casings intended to stuffham and turkey rolls and meat chunk type products. Wieners andfrankfurters are typically smaller diameter products which are subjectedto extremely fast stuffing and peeling operations and utilize fineground meat emulsions. Small diameter nonfibrous casings used forstuffing wiener and frankfurter-type products e.g. to make skinless hotdogs will typically have thin casing wall thicknesses to enableproduction of shirred casing sticks containing greater lengths ofcasing. Typically the thickness or width of the casing wall forproduction of such frankfurter-type sausages will be from about 0.8 toabout 2.0 mils (0.02-0.05 mm), preferably from about 0.9 to about 1.5mils (0.023-0.038 mm).

Typically, fiber-reinforcements such as paper tube will add a thicknessof between about 2.5 and 3.5 mils (0.064-0.089 mm), although thicker orthinner tubes may be employed.

Olefinic oxide polymers such as poly(ethylene oxide) with molecularweights of at least about 70,000 and up to about 5×⁶ are dry,free-flowing white powders, which are substantially completely solublein water at temperatures up to about 98° C. They are substantiallycrystalline materials. Commercially available materials reportedly havemelting points ranging from about 62° to 67° C. as determined by X-rayand NMR standard methods of analysis and polymer densities of from about1.15-1.26 g/cm³. The chemical structure of poly(ethylene oxide) resin is

    (O--CH.sub.2 --CH.sub.2).sub.x

The very high molecular weights of these resins indicate materialshaving extremely small concentrations of reactive end groups resultingin resins having little or substantially no end group reactivity. Asused herein the term "molecular weight" refers to the weight averagemolecular weight (Mw).

Poly(ethylene oxide) is commercially available from Union CarbideCorporation under the trademark POLYOX®. POLYOX® water-soluble resins,CAS Registry No. 25322-68-3, are described as being nonionic watersoluble polymers of poly(ethylene oxide) which are available in a rangeof molecular weights. Referring to the above formula the degree ofpolymerization of POLYOX® resins are disclosed as ranging from "X"having a value from about 2,000 to about 180,000. Further information ofthe properties, functions and uses of POLYOX® resins are disclosed inthe brochure POLYOX® WATER-SOLUBLE RESINS (Copyright 1988, 1990, UnionCarbide Chemicals & Plastics Technology Corporation) which brochure ishereby incorporated by reference in its entirety.

In one embodiment of the invention poly(ethylene oxide) having a weightaverage molecular weight of at least 90,000 is used. Poly(ethyleneoxide) having a weight average molecular weight between about 90,000 and200,000 or between about 100,000 and 4,000,000 may be suitably employed.Higher molecular weight olefin oxide polymers are generally lessexpensive than lower weight materials. For example, in one embodiment anolefin oxide polymer such as poly(ethylene oxide) having a weightaverage molecular weight of at least 1,000,000 has been found to besuitable. Lower weight materials may produce cellulose articles whichare more transparent and have less haze than higher molecular weightmaterials. Preferred olefin oxide polymers have a weight averagemolecular weight which is less than 1,000,000 and most preferably in therange from between 100,000 to 300,000. These materials are easy toincorporate without undue leaching and maintain good optical properties.Preferably the olefin oxide polymers used in the present invention arelinear, especially linear homopolymers and most preferably linearhomopolymers of poly(ethylene oxide).

Fundamental to the present invention is incorporation of an olefinicoxide polymer such as poly(ethylene oxide) in a cellulosic article. Sucholefinic oxide polymer should be of a sufficiently high molecular weightthat it will be retained in the cellulosic article in which it has beenincorporated even though the article may be contacted or washed with asolvent such as water. The amount of olefinic oxide polymer retainedshould be sufficient to impart at least some of the desirable advantagesdescribed below and any amounts which might be leached out in normal useshould be minimal and in any case not destroy the utility of the articlefor its intended purpose.

It is believed that olefinic oxide polymers such as poly(ethyleneoxides) of molecular weights as low as 70,000 may be incorporated incellulose to produce useful articles especially tubular films,preferably tubular food packaging, most preferably sausage casings.These articles are believed to be resistant to leaching out of the oxidepolymer and are further believed to not undesirably suffer from defectsassociated with leaching such as lack of strength which defects may befound in cellulose articles to which lower molecular weight materialssuch as polyethylene glycols (PEGs) having a molecular weight of about20,000 or less have been added. It is believed that poly(ethyleneoxides) (hereinafter also referred to as "PEO") of about 70,000 orhigher molecular weight would retain advantages of the commerciallyavailable higher molecular weight PEO's such as that sold under thetrademark POLYOX WSRN-10.

Poly(ethylene oxides) are used as thickening agents in water. Smallconcentrations of high molecular weight resins can reduce by up to 80%the turbulent frictional drag of the water in which they are dissolved.

It is believed that the improved performance of the cellulosic tubulararticle of this invention is at least partially due to the greaterdimensional stability of the article which is made possible by a uniformdispersion of the olefinic oxide polymer in the tube wall. It appearsthat this compound provides a high rate of moisture absorption duringthe casing finishing operation. For example, it has been observed thatwhen the inventive casing is moisturized immediately prior to high speedshirring-compression, uniform absorption is virtually complete for apoly(ethylene oxide)-containing nonreinforced cellulosic casing by theend of the shirring step and before the final compression in the productshirred stick form. In particular, comparative tests show less shirrsolution left on the mandrel with this casing as compared to anotherwise identical cellulosic casing lacking the poly(ethylene oxide).As a result, the shirred sticks of this invention do not longitudinallyexpand as much as a conventional commercially available nonreinforcedshirred cellulosic casing stick. It is of course well-known that whencellulose is wetted, it swells or grows in size. If the cellulose casingis not completely or uniformly moisturized when it is compressed, theunwetted portions will grow or swell when the moisture subsequentlycontacts these portions.

Another contributing factor to the greater dimensional stability of thiscellulosic tubular article may be that the rapidly uniformly moisturizedarticle forms tighter shirred pleats which hold the stick together. Thatis, the pack ratio of the shirred embodiment of the inventive article ishigher than the pack ratio of an otherwise identical casing shirred andcompressed under equivalent conditions.

Finally, since the conventionally used polyhydric alcohol-type softenermay be avoided with this invention, the mass of the article to becompressed is reduced and this in turn produces stronger pleats.

The as-manufactured cellulosic casing maybe used by food manufacturersin reeled form, but in most instances the casing is pleated, i.e.shirred, and then longitudinally compressed into a compact "stick" form.When this is done, the moisture content is usually raised immediatelyprior to shirring, from a level of about 15% (total weight resin) toabout 30% (total weight basis). Such moisturization raises the watercontent of the cellulose casing to a level suitable for stuffing. Thatis, the deshirred casing may be stuffed by high speed machinery withoutfurther moisturization.

Casings containing an olefinic oxide polymer such as poly(ethyleneoxide) are believed to have a lower co-efficient of friction thansimilar casings not containing an olefinic oxide polymer. Tests of bothstatic and kinetic co-efficients of friction have indicated lower valuesfor uncoated casings containing poly(ethylene oxide) (reported molecularweights of 100,000 and 4 million) relative to both glycerine dipped andnon-glycerine dipped similar casings which do not contain an olefinicoxide polymer. It is believed without wishing to be bound by the beliefthat this lower co-efficient of friction may contribute to improvementsin machinability of the casing during shirring, stuffing and otherprocessing operations.

It has been determined that the inventive casings (semi-finished i.e.after drying but before shirring) containing an olefinic oxide polymerhave increased rates of absorption of water relative to prior artcommercial casings not containing an olefinic oxide polymer. Thus, theinventive casings have a greater rate of absorption both as gel stock(before drying) and after drying. Semi-finished (unshirred) casing madeaccording to the present invention may absorb more water than an equalweight of prior art cellulose casing under similar production conditionsprior to reaching equilibrium although the ultimate equilibriumcapacities may be similar. Changes in relative humidity are not believedto affect the inventive casings any differently than standard commercialprior art casings. Advantageously, the faster rate of absorptionpromotes uniform swelling which contributes to efficient formation ofshirred sticks of casing having uniform physical properties. This alsoprovides greater control and reliability with respect to packaging ofthe shirred sticks. The shirred sticks do not expand or grow in lengthas much as prior art casing and therefore they may be packed moreclosely in boxes and because the sticks weigh less and the same amountof casing may be packed into a smaller space, less expensive and smallerpackages may be used if desired. Additionally, the greater rate ofabsorption allows larger amounts of coatings or additives to beincorporated into the casing in the same or less contact time aspresently used in production. In particular, colorants for self-coloringcasings, peeling aids and liquid smokes may be absorbed at higher ratesreducing equipment needs and allowing for increased process speeds orgreater loading levels at fixed production times.

Beneficially, liquid smokes may be incorporated in casings of thepresent invention. The increased rate of absorption of olefin oxidepolymer containing cellulose casing permits increased loading of liquidsmokes during fixed contact times in production which times aretypically less than that required to saturate the casing. This increasedrate may be beneficially employed to economically produce darker smokecolored casings. Such darker casings have increased eye appeal inmarkets where the meat processor sells the product with the casing lefton. Similar, increased absorption of colorants may produce darkercolored casing or self coloring casing having greater colortransferability. Both tar containing and tar depleted liquid smokes maybe used on both nonfibrous and fiber-reinforced casings. These casingsmay or may not also have other coatings such as peeling aids.Advantageously, acidic, neutralized, or alkaline liquid smokes may beused. In one preferred embodiment for nonfibrous casing, tar-depletedliquid smoke treated casing is made utilizing an acidic tar-depletedconcentrated liquid smoke prepared e.g. in accordance with the teachingof U.S. Pat. No. 4,540,613. Preferably this liquid smoke is externallyapplied to the casing using a dip tank or a foam applicator. This may bedone, e.g. by a process similar to that disclosed in U.S. Pat. No.4,356,218. Preferably the casing will have been treated prior toaddition of the liquid smoke with phosphates to inhibit formation ofblack spots or discoloration e.g. in accordance with U.S. Pat. No.4,511,613. Beneficially, the casing is treated with a base prior toaddition of the acidic liquid smoke such that upon drying of the liquidsmoke treated casing and prior to shirring, the casing has a Ph value offrom about 5 to 6. The descriptions and teachings of U.S. Pat. Nos.4,540,613; 4,356,218; and 4,511,613 are hereby incorporated by referencein their entireties. Suitably, the tar-depleted smoke treated casingswill contain at least 2 mg., and preferably at treated about 5 mg. ormore of smoke constituents per square inch of food casing contact area.Tar containing liquid smokes may also be employed, particularly in fiberreinforced casings. Cellulose casings containing poly(ethylene oxide) aspart of the casing structure according to the present invention may alsobe coated with liquid smoke and/or peeling aid solutions as described inU.S. Pat. Nos. 5,030,464; 4,889,751; 4,377,187; 4,572,098; 4,377,606;4,446,167; 4,442,868; 4,525,397 and 4,104,408.

The pre-shirring moisturization is most commonly accomplished by meansof a spray applied to the casing inner wall. This spray may includeother components as for example humectants such as propylene glycol toretard the rate of water uptake as for example describe in Chiu U.S.Pat. No. 3,981,046, or peeling-aid solutions.

Such peelability enhancing agents include, but are not limited to,carboxymethyl cellulose and other water soluble cellulose ethers, theuse of which is disclosed in U.S. Pat. Nos. 3,898,348 and 4,596,727, thedisclosures of which are incorporated herein by reference in theirentireties; "Aquapel", a Hercules, Inc. trademarked product comprisingalkyl ketene dimers, the use of which is further disclosed in U.S. Pat.No. 3,905,397 issued Sep. 16, 1975 to H. S. Chiu, the disclosure ofwhich is incorporated herein by reference; and "Quilon", an E. I. Dupontde Nemours Co., Inc. trademarked product comprising fatty acid chromylchlorides, the use of which is further disclosed in U.S. Pat. No.2,901,358 issued Aug. 25, 1959 to W. R. Underwood et al., the disclosureof which is incorporated herein by reference.

As previously mentioned above, it is known in the art that ease ofpeeling of the casing, particularly for skinless frankfurters isdirectly related to skin formation and production of a liquid layer orcoating between the casing and the "skin" of the sausage. Under someconditions, peeling the casing from the processed sausage has presentedproblems, particularly in the production of so called "skinless"frankfurters where large numbers of the product are involved andespecially in commercial operations using high-speed automatic stuffingand peeling machines.

When the casing is removed from the meat mass by automatic high-speedpeeling machines, there is occasionally a tendency for some meat toadhere to the casing and be torn from the sausage with the casing,thereby causing surface marring of the sausage. In other instances,variations in the meat emulsion formulations or in the processingconditions can result in a degree of adherence of the casing to theproduct which hinders rapid removal of the casing from product encasedtherein. The use of high-speed, automatic peeling machines in commercialoperations, for example, as disclosed in U.S. Pat. Nos. 2,424,346;2,514,660; 2,686,927; 2,757,409; 3,312,995; 3,487,499; and 3,608,973makes it particularly essential that there be minimal resistance to theseparation of casing from sausage, or the product will jam at the peeleror go through unpeeled. Less than complete removal of the casingnecessitates the expense and inconvenience of hand sorting and peeling.

Heretofore, many attempts have been made to provide casings having easyrelease characteristics. It is known in the art, as disclosed, forexample, in U.S. Pat. Nos. 2,901,358 to Underwood et al., 3,106,471 and3,158,492 to Firth, 3,307,956 to Chiu et al., 3,442,663 to Turbak and3,558,331 to Tarika, that the application of certain types of coating tothe inside wall of food casings may afford improvement in the releasecharacteristics of the casing from the encased sausage product. Use ofpeeling aids or release coatings have helped to overcome thesepeelability problems. Following cooking, cooling and hydrating,water-soluble cellulose ether containing peeling aids help release thecasing from the frankfurter skin by formation of a slippery layerbetween the casing and the frankfurter skin.

Typical water-soluble cellulose ethers which may be employed are thenon-ionic water-soluble alkyl and hydroxyalkyl cellulose ethers such as,for example, methylcellulose, hydroxypropyl methylcellulose,hydroxypropylcellulose, ethyl methylcellulose, hydroxyethylcellulose andethyl hydroxyethylcellulose and preferably the anionic water-solublecellulose ethers such as, for example, carboxymethylcellulose andcarboxymethyl hydroxyethylcellulose. Mixtures of nonionic and anionicwater-soluble cellulose ethers may also be employed. Commercially,carboxymethylcellulose (CMC) and carboxymethylhydroxyethylcellulose arealmost always sold as the sodium salt, and it is well established tradepractice not to refer to the commercial product as the sodium salt. Forthe purpose of this application, reference to these anionic materialsshall include salts thereof e.g. the sodium salt and other alkali metalsales thereof.

The amount of water-soluble cellulose ether present on the internalsurface of the food casing, which is necessary to impart desired releasecharacteristics, can vary over a wide range; though very smallquantities are actually required. In general, tubular casings of thepresent invention will contain at least about 0.001 milligram ofcellulose ether per square inch of casing surface (0.0002 mg/cm²), andpreferably between about 0.002 mg/in² and 0.09 mg/in² (0.0003-0.014mg/cm²) of said cellulose ether. Especially preferred are casings havinga coating on the internal surface thereof between about 0.03 mg/in² and0.07 mg/in² (0,005-0.011 mg/cm²) of said cellulose ether. Greateramounts of the cellulose ether component may be used, if desired,although generally it will not materially improve the releasecharacteristics of the casing and with certain types of meatformulations or processing conditions, fat separation may beencountered.

Peeling aid coatings will typically comprise a release agent such as awater-soluble cellulose ether (as described above) in combination withan anti-pleat lock agent.

Anti-pleat lock agents suitable for use in admixture with peeling aidrelease agents such as water-soluble cellulose ethers to prepare easypeeling coatings on the casings of the present invention includesynthetic, natural, and modified oils including mineral, vegetable andanimal oils such as refined animal and vegetable oils that are normallyliquid at room temperature or have a melting point below about 100° F.,food grade mineral oil, silicone oils and medium chain triglycerides.Also suitable as an anti-pleat lock agent are substances such aslecithin and derivatives thereof. Materials that are or may be placed ina dispersible form in media solutions have been found to be suitable.Typical of this type of material would be, for example, an aqueousemulsion of castor oil or mineral oil. Particularly suitable andpreferred as an anti-pleat lock agent is mineral oil.

By use of the term "anti-pleat lock agent" is meant material which iscapable of promoting deshirring of pleats by minimizing any tendency ofthe pleats of a shirred casing stick to unduly adhere to each other andthereby damage the casing by creation of pinholes, tears or breaksduring deshirring and stuffing. The anti-pleat lock agent willpreferably be effective in the presence of a water-soluble celluloseether such as carboxymethylcellulose which ether is known to promoteadhesion of pleats prior to deshirring.

Suitable amounts of anti-pleat lock agent such as mineral oil will bepresent on the inner surface of the casing in order to effectivelyassist in deshirring and to reduce deshirr forces. Suitable amounts ofan anti-pleat lock agent, preferably mineral oil, may range from about0.05 mg/in² to about 0.3 mg/in² or more (0.008-0.047 mg/cm²), andpreferably will be from 0.1 to 0.2 mg/in² (0.016-0.031 mg/cm²).

Lecithin is an anti-pleat lock agent which may also act as a surfactantwith both wetting and emulsifying properties. It may also promotepeelability of the casing. Lecithin is a mixture of diglycerides ofstearic, palmitic and oleic acids, linked to the choline ester ofphosphoric acid. Most commercial lecithin is a mixture of naturallyoccurring phospholipids which are derived from soybeans. Typical soybeanlecithin comprises the following acids with approximate percentages;palmitic (12%), stearic (4%), palmitoleic (9%); oleic (10%), linoleic(55%) linolenic (4%) and C₂₀ to C₂₂ acids including arachidonic (6%).Lecithin is known to function as a release aid, dispersant, lubricant,softener and to control viscosity in various food industry applications.Lecithin is an amphoteric emulsifier. As used herein, the term"lecithin" includes both unsubstituted lecithin and substituted lecithinwhich has been modified by chemical means and the individualphospholipid constituents thereof, particularly phosphatydylcholine.

Since lecithin may be utilized as an anti-pleat lock agent or possiblyto enhance or potentiate a peeling aid, the amount of lecithin presenton the internal surface of the casing may vary over a wide range. Ingeneral, the preferred tubular casings of the present invention willcontain sufficient lecithin to effectively and favorably impact uponpeelability, and/or the deshirr forces. The water-soluble celluloseether, and lecithin combination, particularly with an anti-pleat lockagent such as mineral oil and a surfactant such as ethoxylatedmonodiglycerides may show improved peelability, relative to peeling aidcompositions without lecithin. Suitable amounts of lecithin may rangefrom about 0.05 to 0.50 mg/in² and preferably range from about 0.1 to0.2 mg/in².

Surfactants suitable for use in the coating compositions on casingsaccording to the present invention include those surfactants which actas wetting agents for the cellulosic casing surface and/or asemulsifying agents for oil such that the surfactant facilitatesdispersion of the coating composition across the surface of thecellulosic casing. Nonlimiting examples of suitable surfactants includewater dispersible or at least partially water-soluble surfactants suchas alkylene oxide adducts of either fatty acids or partial fatty acidesters, for example, ethoxylated fatty acid partial esters of suchpolyols as anhydrosorbitols, glycerol, polyglycerol, pentaerythritol,and glucosides, as well as ethoxylated monodiglycerides, sorbitantrioleate, lecithin, and aliphatic polyoxyethylene ethers such aspolyoxyethylene (23) lauryl ether.

Preferred surfactants include polyoxyethylene sorbitan fatty acid estersor mixtures thereof such as those sold under brand designation Tweensuch as Tween 80 (polyoxyethylene 20 sorbitan monooleate) (commerciallyavailable ICI Americas Inc. of Wilmington, Del.), ethoxylatedmonodiglycerides or mixtures thereof such as those sold under the branddesignation Mazol 80 MGK (commercially available from Mazer Chemical,Inc. of Gurnee, Ill.), sorbitan trioleate (commercially available fromICI Americas Inc. under the brand designation Span 85), and lecithin. Anespecially preferred surfactant is a mixture of ethoxylatedmonodiglycerides such as Mazol 80 MGK. Some surfactants are also knownto act as anti-pleat lock agents e.g. lecithin and Tween 80.

Suitable amounts of a surfactant, such as a mixture of ethoxylatedmonodiglycerides (Mazol 80), may be present on the inner surface of thecasing in order to wet the casing surface and assist in dispersing theanti-pleat lock agent, especially oils, and to emulsify and/or stabilizepeeling aid compositions which contain components of varyingsolubilities. Suitable amounts of a surfactant may range from about0.005 to about 0.06 mg/in² (0.0008-0.0009 mg/cm²) and preferably for asurfactant of ethoxylated monodiglycerides such as Mazol 80 from about0.01 to 0.02 mg/in² (0.002-0.003 mg/cm²). Too little surfactant may leadto an uneven distribution of the coating composition on the casingsurface and with increased surfactant any additional benefits arebelieved to be reduced in significance relative to the added cost orpossible deleterious effect on shirred stick properties such ascoherency, deshirring forces and straightness of the shirred stick.

U.S. Pat. No. 3,898,348 describes the coating of internal surfaces ofcellulose sausage casings with a homogeneous mixture of a water-solublecellulose ether and an additive selected from animal, vegetable, mineraland silicon oils and alkylene oxide adducts of partial fatty acidesters. The coating may be applied to the casing surface in acomposition such that the additive is present in a proportion of about0.1 times the weight of the water soluble cellulose ether and up toabout 0.5 milligrams per square inch of casing surface. Such mixtureshave excellent meat release characteristics and can also effectivelyprotect the casing from "pinholing" failures occasioned by pleatlocking. Easy peeling casings utilizing the release coating have foundbroad commercial acceptance and are presently in use in casingsthroughout the world.

U.S. Pat. No. 4,137,947 to Bridgeford discloses a method of improvingthe meat release (peelability) of cellulose sausage casings by theapplication of a meat release coating to the internal surface thereof.The coating comprises a homogeneous admixture of a water-solublecellulose ether, the partial fatty acid ester of sorbitan or mannitanand a water-soluble polyalkylene ether of the type R(--OC₂ H₄ O)_(n) --Hwherein R represents long chain alkyl radicals having 8 to 16 carbonatoms and n is an integer from 4 to 40. An aqueous coating compositioncontaining the water-soluble cellulose ether, partial fatty acid esterand polyalkylene ether is typically applied to the interior of thesausage casing prior to shirring.

Japanese Patent Application Publication No. 55141(1984) discloses easypeeling coatings which produce casings which are easily deshirredwithout blocking. These coatings comprise a water-soluble celluloseether such as carboxymethyl cellulose and a phospholipid such aslecithin, phosphatidyl choline, phosphatidyl ethanolamine orphosphatidyl inositol. An aqueous coating of the above two componentsmay be used, preferably with an oil and/or a polyol such as glycerin orpropylene glycol.

European Patent Document No. 502,431 discloses peeling aid coatingscomprising mixtures of lecithin with alginate, chitosan and/or casein.

Additionally, European Patent Document No. 468,284 discloses peeling aidcoatings comprising a water soluble cellulose ether and a dextrin andoptionally lecithin.

All of these foregoing peeling aids may be usefully employed on casingsof the present invention.

According to the present invention olefinic oxide polymer may beincorporated with cellulose while the cellulose or a cellulosederivative is dissolved in a solvent. The olefinic oxide polymer, suchas polyethylene oxide may be added to the cellulose starting materialprior to dissolution, but may also conveniently be added e.g. as anaqueous solution to the dissolved cellulose or cellulose derivativeprior to extrusion. This incorporation of the olefin oxide polymer istypically throughout the entire cellulose article if the article is amonolayer film, or throughout at least one layer if the article is amultilayer structure such as may be made by merging a plurality of flowsof a dissolved cellulose or cellulose derivative (such as viscose) priorto solidification of the cellulosic material (by such means as is knownin the art e.g. coagulation, regeneration or precipitation). When mergedflows of dissolved cellulosic material are extruded, for example as forcoating an inside and outside surface of a paper tube in the manufactureof fiber reinforced cellulose casing or for making nonfibrous multilayerarticles, at least one of the layers (preferably the inner surfacelayer) will have an olefinic oxide polymer such as poly(ethylene oxide)uniformly dispersed therein. Means for producing such articles havingmultiple coats or layers are disclosed e.g. in U.S. Pat. Nos. 3,661,621;3,709,720 and 2,141,776 which patents are hereby incorporated byreference.

The amount of olefin oxide polymer such as PEO which is incorporatedinto the cellulosic article may vary over a wide range; though onlysmall quantities are actually required. In general, cellulosic articlesof the present invention such as seamless tubular food casings areformed by addition of at least about 0.5% of olefin oxide polymer basedupon the bone dry weight of the cellulose article.

In the manufacture of nonfibrous regenerated cellulose casings by theviscose process, typically viscose is extruded through an annular dieinto a coagulating and regenerating bath to produce a tube ofregenerated cellulose. This tube is subsequently washed, plasticizede.g. with glycerine, and dried e.g. by inflation under substantial airpressure. After drying, the casing is wound on reels and subsequentlymay be shirred. Fibrous casing employs a similar process of manufacture.However, the viscose is coated on one or more sides of a tube which isgenerally formed by folding a web of paper so that the opposing sideedges overlap. The viscose impregnates the paper tube where the viscoseis subsequently coagulated and regenerated to produce a fiber-reinforcedtube of regenerated cellulose.

Referring by way of example to use of the viscose process in the presentinvention, the olefinic oxide polymer may be added to the sheetcellulose e.g. as a powder or in granular form, or may be added latere.g. during the steeping, shredding or aging steps. It may also be addedto the xanthated cellulose or the dissolved cellulose xanthate(viscose). Additions of the olefinic oxide polymer prior to viscoseformation may be advantageously employed to promote uniformity ofincorporation, and allow introduction of greater amounts of oxidepolymer without undesirable dilution. It is believed that addition ofthe oxide polymer to the cellulose xanthate prior to viscose formationmay allow the greatest flexibility in processing. For example, the oxidepolymer may be added with aqueous sodium hydroxide and cellulosexanthate to the vissolver (a vessel for dissolving cellulose xanthate)to form viscose. Amounts of oxide polymer may easily be adjusted todesired levels and the vissolving process allows for adequate mixing toassure uniformity of incorporation of the oxide polymer in the viscose.Also, the oxide polymer may be introduced to the formed viscose prior toextrusion by forming an aqueous solution of oxide polymer and meteringthe solution into the viscose with appropriate mixing to assure auniform product. The above is further illustrated in the drawings.

Referring now to FIG. 1, cellulose starting material in the form ofsheets of pulp 10 and an aqueous solution of sodium hydroxide 11 arebrought into contact in a steeping bath 12 to convert the cellulose toalkali cellulose. As noted above, typically high quality cellulose pulphaving a density between about 0.8-0.9 g/cm³ is used with a 17-20 weightpercent aqueous solution of sodium hydroxide. Cellulose is held in thesteeping bath for about 50-60 minutes at a bath temperature of about19°-30° C. The steeping bath is drained and the alkali cellulose pressedas described in further detail above. The pressed alkali cellulose istransferred to shredding means such as a temperature controlledmechanical shredder 14 where the alkali cellulose fibers are pulledapart. The shredded alkali cellulose is aged for a suitable time toproduce the desired degree of polymerization and then transferred to abaratte 16 to which CS₂ is added to convert the alpha cellulose tocellulose xanthate. The cellulose xanthate 18 is then transferred to avissolver 19 with addition of aqueous sodium hydroxide 20 and thetemperature is controlled and mixture agitated to place the cellulosexanthate into solution thereby forming viscose. The formed viscose 21 isallowed to ripen to achieve the desired xanthation, deaerated, filteredand conveyed via pumping means such as a viscose pump 22 and transfermeans such as pipe 23 to mixing means such as a static mixer 24. Anolefinic oxide polymer 25 such as poly(ethylene oxide) may be added as ametered solution to the static mixer 24 which contains a series ofbaffles to facilitate mixing of the olefinic oxide polymer 25 andviscose 21. The viscose 21 and poly(ethylene oxide) 25 are preferablyuniformly mixed to produce a homogeneous solution which is transferredby transfer means 26 such as a pipe to an extrusion die or nozzle 27which immediately opens into coagulation and regeneration means such asa tank hereinafter referred to as an aquarium 28 containing an acid suchas sulfuric acid which initiates and causes coagulation and regenerationthereby forming a shaped article. The aquarium may also contain agentsto modify the rate of regeneration, such as metal salts, as is wellknown in the art. It will be appreciated that various forms of diesknown in the art may be used. In fiber manufacture, the die 27 comprisesspinnerets. In tubular film manufacture, such as for sausage casing, thedie has an annular opening. For production of flat film or sheets thedie may be a slot. Also, coextrusion dies may be employed as well asdies for coating opposing sides of a cellulose or plastic papersubstrate.

Optionally, a fiber web of e.g. paper 29 may be admitted to die 27 wherethe viscose is extruded onto the paper before it enters the aquarium.Different dies are used for production of nonfibrous and fibrous casingand suitable dies are well known in the art. In the production offiber-reinforced sausage casings the paper is shaped into a tube priorto coating with viscose. The viscose is allowed to penetrate the paperprior to admittance to the aquarium and penetration time may be adjustedby modifying the distance between the die and aquarium and/or adjustingthe travel speed of the article.

Optionally, the olefinic oxide polymer may be added to the cellulose,cellulosic solution or cellulose derivative at any point prior to theextrusion or shape forming step as long as the poly(ethylene oxide)becomes sufficiently mixed to produce a homogeneous mixture atextrusion. It should be clearly understood that such addition ofolefinic oxide polymer may be made at various points prior to extrusionregardless of the process utilized to create an extrudable cellulose orextrudable cellulose derivative including the aforementionedcuprammonium, N-methyl-morpholine-n-oxide, zinc chloride, and cellulosecarbamate processes as well as the well known viscose process which ispresented here as a preferred example of the applicable processes.Referring again to FIG. 1 of the drawings, the poly(ethylene oxide) 25is preferably added as an aqueous solution to the viscose via a staticmixer 24. However, the olefinic oxide polymer 25 may also be added as apowder or in solution to the pulp sheets 10 or aqueous sodium hydroxide11 prior to or during steeping. It may also be added prior to or duringshredding as well as prior to or in the baratte or vissolver. It isbelieved that addition prior to viscose formation, particularly to thevissolver by addition to the sodium hydroxide, may provide certainadvantages of cost and efficiency. For example, by adding the polymeradditive to the vissolver, mixing may be performed in existing equipmentwithout requiring a separate mixer such as the static mixer.

Extrusion of viscose through die 27 into the aquarium 28 produces apartially coagulated and regenerated cellulosic article which isconveyed by transfer means 30 to additional acid regeneration means 31such as one or more consecutive tubs of acid. The regenerated cellulosicarticle, by way of example, may be a tube which is then conveyed bytransfer means 32 to washing means 33 such as one or more consecutivetubs of water which may also contain additives such as caustic e.g. toadjust pH and facilitate removal of sulfer by-products. The washedarticle of regenerated cellulose is conveyed by transfer means 34 todrying means 35. Optionally, the article may be conveyed by transfermeans 34a to plasticizing means 36 such as one or more tubs containing asuitable plasticizing agent, for example, an aqueous solution of one ormore polyols such as glycerine and from the plasticizer means 36, thearticle may be conveyed via transfer means 37 to the drying means 35.Drying means 35 may be humidity controlled hot air dryers where themoisture content of the formed article such as a tube of cellulosiccasing is adjusted. One of the advantages of the present invention isthat the plasticizing means 36 (commonly a tub containing 5-10% of apolyol such as glycerine in water) is unnecessary and may be omitted.Cellulose films made according to the present invention are sufficientlystrong and flexible without requiring any additional polyol orplasticizer. This is a significant advantage in the manufacture ofshirred casing. For example, cellulosic sausage casing may be made wherethe olefinic oxide polymer replaces a portion of the cellulose in thecasing yet the resultant casings may have of normal moisture content andbe sufficiently flexible and not brittle even though no additionalsoftener or plasticizer has been added. This means that the cost of theglycerine or other plasticizing agent is saved, that the casing weighsless due to omission of the glycerine (thereby saving on shippingcosts), and that a thinner casing (thinner because it is uncoated withglycerine) having less mass per unit area may be utilized to producemore compact shirred sticks. Advantageously, either a greater length ofcasing may be shirred to a set shirred stick length relative to presentcommercial casing containing glycerine, or an equal casing length may beshirred to a shorter shirred stick length.

Referring again to the drawings, the dried, moisture adjusted casing isconveyed via transfer means 38 to collection means 39 such as a take-upreel or shirring operation. Typical transfer means 30,32,34,37 and 38may each comprise one or more rollers.

The present invention is particularly beneficial in the production ofnovel shirred sticks of tubular casing. Shirring techniques for thecasings described herein generally involve the continuous feeding of alength of flat casing feed stock, from a reel for instance, into ashirring machine where the casing is inflated with low pressure gas,usually air. The inflated casing is passed through an array of shirringrolls which pleat the casing up against a restraint on or about theshirring mandrel until a preselected shirred length has been attained.For a floating mandrel type of shirring machine, such as described inU.S. Pat. No. 3,766,603 for example, the shirred casing is thentransferred linearly past or away from the restraint against which theshirring was performed and onto an extended mandrel portion wherein itis compacted into a desired stick length. For a withdrawing mandrelshirring machine such as described in U.S. Pat. No. 2,583,654 forexample, the shirring mandrel with the shirred casing remaining thereonis rotated to an alternate position where the shirred casing iscompacted into a desired stick length.

The normal compaction results in a stick length which may be from about0.8 percent to about 1.2 or 1.3 percent of the original casing length.

The ratios of original casing length to shirred stick length, referredto as "pack ratio", have been generally on the order of 70 to 125throughout the industry, prior to the time of the present invention.

Packing efficiency is another way of quantitatively expressing theextent to which original casing lengths are compacted in the shirredstick form. Packing efficiency is defined as the ratio of the volume ofthe shirred and compacted casing in a unit length divided by the volumeof the same unit length which would be occupied by solid casingmaterial, and it may be determined by the following relationship:##EQU1## where PE=Packing Efficiency

Lc=casing length

Ls=shirred casing stick length

FW=casing flat width

tc=casing wall thickness

OD=shirred casing stick outer diameter

ID=shirred casing stick inner diameter

This computation automatically takes into account the specific gravity,and/or density of the casing material itself. Inspection of therelationship shows that the ratio is actually the volume of the casingflat stock which is contained in the shirred casing stick, divided bythe volume of a hollow cylinder having the same dimensions as theshirred casing stick. The extent to which packing efficiency increasesis thus measuredly the closeness of its approach towards one (1), unity.

Since pack ratio is the ratio of Lc to Ls, another way to express thepacking efficiency relationship is as follows: ##EQU2##

It can be seen that for a given packing efficiency, the pack ratiovaries with the difference between the outside diameter and the insidediameter of the stick of a given size casing. Further, since the outsidediameter is necessarily limitedly the flat width (FW) of the casing usedto form the stick, increasing the diameter difference to increase thepack ratio must decrease ultimately the size of the bore or insidediameter. While the objectives of maximum stick bore and maximum packratio work against each other, the fact remains that packing efficiencyis maximized at a given pack ratio when the stick inside diameter ismaximized.

It is usually desirable to utilize the maximum bore size (internal crosssectional area) stuffing horn with a given casing size, in part tomaximize throughput and minimize stuffing pressure. Another reason tomaximize the horn size is to eliminate the danger of "fatting out".Fatting out is a phenomenon which arises when the passage of the meatemulsion through a stuffing horn at a high shear rate causes theemulsion to break down and allows water and fat to separate out. Thewater and fat thereafter accumulate between the surface of the finishedsausage product and the cellulosic food casing during processing, tothereby produce an unsatisfactory sausage product having an unacceptablevisual appearance. The shear rate decreases with increasing stuffinghorn inner diameter.

The goals that have been sought in shirring technology have been toproduce a casing stick which can be deshirred and stuffed on a stuffingapparatus, continuously, with no mechanical defects or breakdowns so asto insure continuous production, the stick itself having sufficientstructural and mechanical integrity, i.e. coherency, to withstand theordinary rigors of packaging, storage, handling and placement on thestuffing apparatus, and, in addition, the desideratum of compacting asmuch stuffable casing into a given stick length as is technicallyfeasible for use on a stuffing horn of maximum possible bore size.

Accordingly, the "ideal" casing stick is one of high coherency,balancing a long length of casing per unit stick length (high packratio) and a large inner diameter or bore size (high packingefficiency).

An important factor affecting the suitability of shirred casing sticksfor use with automatic food stuffing equipment, for example employed inthe preparation of products such as frankfurters, is the durability orcoherency of the shirred stick as a self-sustaining article. Adisjoinder or break in the shirred stick prior to mounting on thestuffing apparatus may make the stick unsuitable for use. Accordingly,any modification to a tubular food casing that is to be formed intoshirred casing sticks must be considered in light of its effect oncoherency. Advantageously, shirred sticks of casing made according tothe present invention have sufficient coherency to hold together fromimmediately after shirring through shipping and ultimate use, whileallowing the shirred casing to be easily deshirred during stuffingoperations without production of casing defects such as holes or tearingand without requiring undue force thereby minimizing such defects.

Following is a description of the coherency test that is used fordetermining this important characteristic of shirred casing sticks ofthe present invention.

COHERENCY TEST METHOD

Coherency (COH) of a casing stick is determined by measuring the bendingmoment in inch-pounds at the breaking of a stick. A casing stick iscradled on two V-notched support brackets secured on a base plate andspaced apart a distance (D) about 80% to 90% of the length of the casingstick being tested. A pressure member having V-notched struts spacedapart a distance of D less 4 inches is centrally lowered onto the top ofthe casing stick. A downward pressure is provided by lowering a forcegauge (such as Chatillon Digital Force Gauge, Model DFG-10 with a "Holdat Maximum Device"), that is secured centrally to the pressure member ata constant velocity of about 81/2 inches per minute. The force isincreasingly applied until the casing stick breaks. The maximum forcereading P in pounds is noted. The bending moment in inch pounds at breakon the apparatus is equal to P/2×2 inches, and thus the force reading Pequates to inch-pounds of bending moment to break the casing stick. Ingeneral, a coherency of at least about 1.0 inch-pound (1.2 cmKg) isrequired to provide shirred sticks of sufficient integrity to survivenormal packaging and handling operations from the time of shirring untiluse on a stuffing machine, a coherency of at least about 2.0 inch-pounds(2.3 cmKg) is desirable, and at least 2.5 inch-pounds (2.9 cmKg) isespecially suitable and preferably at least 3.0 inch-pounds (3.5 cmKg)is achieved.

Since the relationship of usable casing stick bore diameter with respectto stuffing horn diameter is a most meaningful measure of casing articlefunctionality, a "drop fit" (also termed "horn fit") test has beendeveloped for use with shirred casing articles. To simulate the placingof a shirred stick on a stuffing horn and thereby measure the effectiveinternal diameter of the shirred stick, a test was designed wherein ashirred stick is placed over the upper end of a vertical stainless steelrod of longer length than the shirred stick and allowed to freely fallunder its own weight completely around said rod to its lower end. Moreparticularly, the rod may be vertically positioned on a table. Theshirred stick is placed over the rod upper end and then released. If thestick falls to the table surface, the drop fit test is successful. Rodsare available in diameter increments of 0.010 inches, and for certaincasing size ranges, rods have been fabricated in 0.002 inch increments.The shirred stick is tested on each rod beginning with the smallest rodand on each succeeding size rod until the shirred stick will not freelyfall over the entire length of the rod. The largest diameter rod overwhich the stick freely falls for its entire length is the effectiveinternal diameter of said shirred stick, i.e., the "drop fit" or "hornfit" diameter.

In the manufacture of shirred cellulosic casing sticks, the individualsticks vary slightly in bore size, in part due to irregularities inextensions of pleats within the stick bore. For this reason, forexperimental work, it is necessary that multiple shirred sticks, bemeasured for drop fit and the arithmetic average used to determinefunctionality of the entire group in terms of the stuffing horn fit.Unless indicated otherwise, the reported value for drop fit (horn fit)is an average for 10 sticks. As previously indicated, drop fit averagesare preferably to the thousandth of an inch, and a drop fit requirementis defined to this degree of accuracy. For example, if the requirementis 0.490 inch minimum, an average drop fit of 0.489 inch would beunacceptable, since a significant number of sticks in the grouprepresented by the 0.489 inch average drop fit measurement would not befunctional on a 0.490 inch diameter stuffing horn.

Another factor that is important in affecting the suitability of shirredcasing sticks for use with automatic food stuffing equipment is thedeshirring force required to deshirr the casing. If the requireddeshirring force is excessive, tearing of casing will result duringdeshirring. A deshirring force test, as described below, was employed inevaluating the coated casings of the present invention.

Deshirring Force Test

This test was used to determine the force required to deshirr a selectedstick of casing in the direction in which it would be stuffed. Theapparatus used consists of a force gauge (Model DFG-2, Chatillon DigitalForce Gauge, measuring from 0 to 2 pounds in 0.001 lb. increments) and apulley with an attached reeling device which is used to pull and deshirrthe casing from the shirred stick. Using this equipment, a casing stickis pulled and deshirred at a constant speed of about 60 inches perminute.

The test procedure for the deshirring force tests consists of thefollowing steps:

(a) From the selected shirred stick, an approximately 2 inch (3 cm)sample is removed from the open end, the middle, and the closed end ofthe stick.

(b) The closed end disposed portion of each stick sample is deshirred byhand approximately 1 inch (2.5 cm). Then the open end disposed portion(cone portion) of each stick is wrapped with adhesive tape to ensurethat the casing will not deshirr at that cone position and to provide atab for clamping.

(c) The deshirred portion of the stick is clamped to the force gaugeusing a spring clamp which is attached to the gauge. The other (taped)end of the stick is clamped to the reeling device attached to thepulley.

(d) The reeling device and pulley mechanism is started and the casingdeshirring begins. A chart recorder continuously records measurements ofthe deshirring force on the force gauge. The minimum values obtained foreach section of the shirred stick are averaged as are the maximum valuesand the test is repeated with two additional sticks of casing. The nineminimum values obtained are averaged to provide the average minimumdeshirr force. Also, the nine maximum values measured are averaged andreported as the maximum deshirr force.

The maximum deshirr force is an indication of the likelihood of failureof a shirred stick during stuffing operations. High speed deshirringupon stuffing with automatic stuffing equipment is likely to causetears, breakage or pinholes in casing exhibiting excessively highdeshirr forces.

Actual deshirr force values of casing will vary depending upon such wellknown parameters as casing diameter and type and size of shirringpleats, as well as the presence, type and amount of any coating on thecasing.

The invention will become more clear when considered together with thefollowing examples which are set forth as being merely illustrative ofthe invention and which are not intended, in any manner, to belimitative thereof. Unless otherwise indicated, all parts andpercentages are by weight. Also, when mixtures are said to be completelydissolved, such description is based upon a visual examination of thesolution by eye. Casing flatwidth is the width of a tubular casing whichhas been pressed flat. The circumference of a tubular casing is equal totwo times the flat width.

Unless otherwise noted, the physical properties reported in the examplesbelow were measured by either the test procedures described above ortests similar to the following methods.

Bone Dry Gauge (BDG)

Bone dry gauge is the weight per unit length of cellulose film or casingfor a known width of casing which has been washed in water to removewater leachable constituents and then dried at elevated temperatures toremove moisture. For a given flatwidth of casing Bone dry gauge is theweight per unit length of bone dry cellulose plus any constituent whichis not leached out by washing in water. Such nonleachable constituentsare considered to be fixed in the cellulosic structure of the film orcasing.

Determination of Bone Dry Gauge is made by cutting a sample 40 inches inlength of a determined width. In all of the examples herein BDG fornonfibrous casing was determined using two pieces of casing each being20 inches (50.8 cm) long. BDG for fibrous casing was determined using asingle 10 inch (25.4 cm) long piece of casing.

Each tubular casing sample is slit lengthwise to produce a sheet of filmwhich is then placed in a wash rack and washed for 1 hour usingcountercurrent washing to remove any water leachable constituents fromthe casing.

After washing for 1 hour the casing is subsequently placed in a beakerand dried in a convection oven set at a temperature of about 110° C. forat least about 1 hour to drive off moisture. The beaker containing thedried samples is removed from the oven and placed in a dessicator andallowed to cool to room temperature. The dried, cooled samples are thenplaced in a tared weighing bottle and the weight of the casing ismeasured and recorded. The flatwidth of the casing is also recorded. BDGis reported as the dried weight of the casing per unit length for aknown flatwidth of casing. Although casing lengths were measured ininches, the data presented in the examples have been converted to metricunits.

Burst Stress Test For NonFibrous Film

A sample comprising an approximately 18 inch (46 cm) length of tubularnonfibrous film (casing) is obtained and soaked in room temperaturewater for at least about 30 minutes. This simulates conditions of use,for example, in sausage processing operations where casings are exposedto moisture and water in a variety of steps. The dry and wet flatwidthof the casing may be measured and recorded. One end of the casing isclamped shut and the other end is secured about an air nozzle. Thecasing is inflated with air from the nozzle. The diameter of the casingis measured at various pressures as the air pressure inside the inflatedcasing is continuously increased until the casing ruptures (bursts). Thepressure and diameter at the bursting point is noted. A second sample issimilarly tested and the average values for both samples are reported.

Burst Stress Test For Fibrous Film

A sample comprising an approximately 30 inch (76 cm) length of tubularfibrous film (casing) is obtained and soaked in room temperature waterfor at least about 30 minutes. This simulates conditions of use, forexample, in sausage processing operations where casings are exposed tomoisture and water in a variety of steps. The dry (before soaking) andwet flatwidths of the casing are also measured and recorded. One end ofthe casing is tied shut and the other end is secured about an airnozzle. The casing is inflated with air from the nozzle. The diameter ofthe casing is measured at various pressures as the air pressure insidethe inflated casing is continuously increased until the casing ruptures(bursts). The pressure and diameter at the bursting point is noted. Asecond sample is similarly tested and the average values for bothsamples are reported.

The following ASTM test methods may also be utilized to test materialsor properties of the inventive films.

Molecular Weight Distribution: ASTM D-3593

Polyol/glycerine: ASTM-0615

All ASTM test methods noted herein are incorporated by reference intothis disclosure.

The above description and following examples are given to illustrate theinvention and methods of making the invention, but these examples shouldnot be taken as limiting the scope of the invention to the particularembodiments or parameters demonstrated since obvious modifications ofthese teachings will be apparent to those skilled in the art.

EXAMPLE A

A 10% by weight aqueous solution of poly(ethylene oxide) (hereinafterPEO) was added to a stream of viscose via a pigmentor apparatus justprior to extrusion.

The PEO-containing viscose was extruded into a seamless tube, coagulatedand regenerated according to well known procedures in the art of makingregenerated cellulose casings. The tube of regenerated cellulose had aflat width of approximately 3.3 cm. The PEO used in this example was acommercially available powder sold under the trademark POLYOX WSRN-10 byUnion Carbide Corporation. The poly(ethylene oxide) was added to theviscose at a rate of about 25 cm³ /min. The extruded tube was observedto regenerate faster and by-products washed out faster relative to asimilarly processed tube of regenerated cellulose not having PEO. ThePEO-containing casing also absorbed more moisture than similarly madecasing not having PEO. Also, the dried PEO-containing casing appearedmore transparent and glossier than casing made without PEO.

EXAMPLE 1

Example 1 describes preparation of solutions A-F which were utilized infollowing Examples. Six solutions (A-F) were prepared as follows. In theExamples, all percentages are by weight unless indicated otherwise. Allof the POLYOX and PEG resins were commercially supplied in powderedform. POLYOX WSRN-10, POLYOX WSR-1105, POLYOX WSR-301 and PEG 10,000 areall trademarks of Union Carbide Corporation. CORCAT P-600 is a trademarkof Cordova Chemical Company. The poly(ethylene oxide), poly(ethyleneglycol) and poly(ethyleneimine) aqueous solutions prepared below wereall determined by a visual examination to be completely dissolved.

A. A 15% by weight solution of Union Carbide POLYOX WSRN-10, (a 100,000molecular weight poly(ethylene oxide) homopolymer) was prepared bymixing 90 grams of WSRN-10, in 510 grams of water using a Waringblender. The mixture was blended at high speed for 15 minutes. Theresulting solution was foamy but upon sitting gave an opaque solutionwith no undissolved POLYOX.

B. An 8% by weight solution of Union Carbide POLYOX WSRN-10, (a 100,000molecular weight poly(ethylene oxide)homopolymer) was prepared by mixing240 grams of WSRN-10, in 2760 grams of water using a propeller type labmixer. The solution was mixed until all of the WSRN-10 was in solution(about 3 hours).

C. A 5% by weight solution of Union Carbide POLYOX WSR-1105 (a 900,000molecular weight poly(ethylene oxide) homopolymer) was prepared bymixing 150 grams of WSR-1105 into 2850 grams of water using a propellertype lab mixer. The solution was mixed until the WSR-1105 was insolution (about 5 hours).

D. A 1% by weight solution of Union Carbide POLYOX WSR-301 (a 4,000,000molecular weight poly(ethylene oxide) homopolymer) was prepared byheating 2970 grams of water to 60° C. and slowly adding 30 grams ofWSR-301 to the heated water using a propeller type of mixer foragitation. The solution was mixed for five hours until the WSR-301 wascompletely dissolved. The solution was allowed to cool to roomtemperature prior to use.

E. A 7.5% by weight solution of Union Carbide PEG 10000 (a 10,000molecular weight poly(ethylene glycol)) was prepared by mixing 225 gramsof PEG 10000 into 2775 grams of water using a propeller type lab mixer.The solution was mixed until the PEG 10000 was completely dissolved.

F. A 7.5% by weight solution of poly(ethyleneimine) was produced bymixing 775 grams of Cordova Chemical Company CORCAT P-600 (a 40,000 to60,000 molecular weight poly(ethyleneimine) which is commercially

available as an aqueous solution containing 33% solids) into 2225 gramsof water using a propeller type lab mixer. The solution was mixed forone hour until the CORCAT P-600 was completely dissolved.

G. A 2% by weight solution of Union Carbide POLYOX WSR-301 (a 4,000,000molecular weight poly(ethylene oxide) homopolymer) was prepared byheating 2940 grams of water to 60° C. and slowly adding 60 grams ofWSR-301 to the heated water using a propeller type of mixer foragitation. The solution was mixed for five hours until the WSR-301 wascompletely dissolved. The solution was allowed to cool to roomtemperature prior to use.

EXAMPLE 2A-2F

A non-fibrous cellulosic casing was produced by a typical viscoseprocess modified to include a static mixer in line between the viscosepump and the nozzle. The static mixer was an approximately 18 inch (46cm) long pipe of one inch (2.54 cm) inner diameter with an inlet nozzleon one end of the outside wall that allows a second liquid to beintroduced into it. The inside of the pipe contains a series ofhorizontal and vertical baffle rings which form a criss-cross patternthrough the pipe which facilitates mixing of the two liquids as theytravel from an entrance end of the pipe to the common exit at theopposing end of the pipe.

As viscose flows through the pipe, a second liquid is admitted anduniformly mixed into the viscose by dividing and redividing the viscoseand solution additive as they pass through the baffles. The viscose andadded liquid form a homogeneous solution that is then extruded through anozzle and regenerated in the usual manner. This viscose processutilized starting materials and process conditions believed to produce aregenerated cellulose having a weight average molecular weight (Mw) ofover 100,000. Typical fibrous and nonfibrous casings are commerciallymade with regenerated cellulose having a Mw of from about 80,000 to150,000.

An aqueous solution of polyethylene oxide (PEO) made substantially asdescribed for Solution A in Example 1 was continuously added to aviscose stream via a static mixer as described above. The flow ratios ofthe viscose and Solution A were adjusted to provide films havingcellulose and polyethylene oxide contents as indicated in Table 1.Examples 2A and 2D are control examples (not of the invention) in whichno solution additive was introduced. The viscose flow was the same ratefor Examples 2A and 2B, but was reduced 5% for Example 2C relative toExamples 2A and 2B. The viscose flow was reduced 10% for Examples 2D and2E relative to Example 2A. The viscose flow for Examples 2D and 2E wasthe same.

Example 2F is a control example for comparative Example 2G (not of theinvention) in which an aqueous solution of poly(ethylene glycol) madesubstantially as described for Solution E in Example 1 was continuouslyadded to a viscose stream via a static mixer in a manner similar to thatdescribed above for addition of PEO. The flow ratios of the viscose andSolution E were adjusted to provide film having the cellulose andpoly(ethylene glycol) content indicated in Table 1. In control Example2F (not of the invention) no solution additive was introduced.

                                      TABLE 1                                     __________________________________________________________________________                             Polymer                                                   Solution   Weight   Additive                                                                            Cellulose                                                                              Cellulose                                                                           Polymer                              Additive   Ratio of mg/cm % Polymer                                                                              Content                                                                             Additive                        Example                                                                            Type of                                                                            Flatwidth                                                                           Cellulose to                                                                           Calc.                                                                            Calc.                                                                            Additive mg/cm                                                                         mg/cm Retained in                     No.  Polymer                                                                            cm    Polymer Additive                                                                       add.                                                                             ret.                                                                             measured***                                                                            Calculated                                                                          Cellulose                       __________________________________________________________________________                                                  %                               2A   --   2.74  100:0    -- -- 13.48    --    --                              2B   PEO* 2.79  100:10   1.49                                                                             1.19                                                                             14.67    13.48 80                              2C   PEO* 2.79  95:15    2.23                                                                             1.90                                                                             14.71    12.81 85                              2D   --   2.79  100:0    -- -- 12.11    --    --                              2E   PEO* 2.84  100:20   2.97                                                                             2.60                                                                             14.71    12.11 88                              2F   --   3.40  100:0    -- -- 19.24    --    --                              2G    PEG**                                                                             3.40  95:5     0.96                                                                             0.67                                                                             18.95    18.28 70                              __________________________________________________________________________     *Poly(ethylene oxide) commercially available from Union Carbide Corp.         under the trademark Polyox WSRN10 having a reported average molecular         weight of 100,000.                                                            **Polyethylene glycol commercially available from Union Carbide Corp.         under the trademark PEG 10000 having a reported average molecular weight      of 10,000.                                                                    ***Measured as Bone Dry Gauge (BDG) of casing.                           

Referring to Table 1, Examples 2A, 2D and 2F were control examples (notof the invention). These control examples were seamless, nonfibroustubular films of regenerated cellulose which were formed, plasticizedwith glycerine and moisturized to produce an article suitable for use asa sausage casing. In examples 2B, 2C and 2E of the inventionpoly(ethylene oxide) having a reported average molecular weight of100,000 was added as a 15% aqueous solution. The flow rates of theaqueous solution of polymer additive and viscose were adjusted to yieldthe indicated weight ratio of cellulose to polymer additive. The valuesof poly(ethylene oxide) and poly(ethylene glycol) reported in Table 1 as"Polymer Additive calculated as added" were calculated using the knownsolutions from Example 1 and flow rates. The Bone Dry Gauge (BDG) wasmeasured by a method similar to that described above. For controlExamples 2A, 2D and 2F it is known that in the viscose process which wasused substantially all of the cellulose is regenerated from the viscoseand that the washed casing is substantially pure cellulose. For thesecontrol examples, the BDG is equal to the Bone Dry Cellulose weight. ForExamples 2B, 2C and 2E and comparative Example 2G the BDG includes boththe weight of the cellulose and the weight of the polymer additiveincorporated in the cellulose. The amount of polymer additive retainedin the cellulose casing after washing with water was calculated as thedifference in the values for BDG and calculated cellulose content. Thisvalue is further reported as the percentage of polymer additive retainedin the cellulose. The viscose flow was unchanged between Examples 2A and2B and also between Examples 2D and 2E giving rise to the calculatedcellulose content for Examples 2B and 2E. The viscose flow for Example2C was 95% of that for 2A. Similarly the viscose flow for Example 2G was95% of that for Example 2F giving rise to the calculated values reportedin Table 1. As demonstrated by the data presented, a much greaterpercentage by weight (30%) of the low molecular weight PEG does notremain as part of the casing relative to the higher molecular weightpoly(ethylene oxide) (12-20%). This example demonstrates that whenmaterials such as water soluble PEG having a substantially lower averagemolecular weight than the cellulose are added prior to extrusion, asubstantial proportion of the water soluble low molecular weightmaterial is not securely connected or incorporated with the cellulose,but is easily removed by washing with water. In contrast, highermolecular weight olefinic oxide polymers such as poly(ethylene oxide)having an average molecular weight of 100,000 are substantiallyincorporated or securely connected to the cellulose and not easilyremoved by washing with water. It is believed that materials such asolefinic oxide polymers which have average molecular weightssubstantially less than the average molecular weight of the cellulose inthe desired cellulosic article tend to leach or wash out to anundesirably large extent. In this example, the cellulose was believed tohave an average molecular weight (Mw) of between about 100,000- 120,000,the PEG had a reported Mw of about 10,000 and the PEO had a reported Mwof about 100,000. Substantial amounts of the water soluble PEG wereeasily washed out by water whereas unsubstantial or minor amounts of thewater-soluble PEO were removed by washing. It is believed withoutwishing to be bound by that belief that leaching out of high amounts ofpolymer may lessen or impair the strength of the article produced,especially film articles. For many useful articles of the invention itis believed to be desirable that the amount of olefinic oxide polymerretained or incorporated in the cellulosic article be greater than thatexhibited by comparative Example 2G, preferably at least about 75% andmore preferably at least about 80% or more will be incorporated and noteasily washed out by contact with water or the typical aqueous washingsolutions which are well known and utilized in casing manufacture suchas in the viscose process. It is believed that water soluble olefinicoxide polymers such as poly(ethylene oxide) having average molecularweights of at least about 70,000 may be usefully employed in variousembodiments of the invention.

EXAMPLES 3A-3C

Laboratory film samples of regenerated cellulose containingpoly(ethylene oxide) and poly(ethylene glycol) were prepared fromviscose and tested for leaching of the PEO and PEG. The PEO and PEGpolymer additives were prepared as described above in Example 1 forsolutions B and E respectively. The viscose was similar to thatdescribed above in Example 2. Cast films were made by uniformly mixing ameasured amount of each solution additive with viscose and drawing downthe viscose/additive mixture on a glass plate using a Bird applicatorsuch as that described in U.S. Pat. No. 2,151,183 having a 20 mil gapbetween the surfaces of the glass and the spreading edge of theapplicator. For each Example 3A-3C, the glass plate (coated with anapproximately 20 mil thick layer of viscose) was set into acoagulation/regeneration bath comprising an aqueous solution of sulfuricacid (13.1%) and sodium sulfate (25.5%).

The viscose was allowed to coagulate for about 3 minutes and then theglass plate and the regenerated cellulosic film were removed from thebath. About 10 to 15 cast films were made for each of the Examples 3A-3Creported in Table 2. The regeneration bath was changed for each Example3A-3C, but all films made for a particular example used the same singlebath. Thus, for Example 3A about 10-15 cast films containing 17%poly(ethylene oxide) and 83% cellulose were regenerated in acidicregeneration bath. The weights of the acid bath solution employed andthe total weight of the viscose (including polymer additives) which wasregenerated are reported in Table 2. Following regeneration of the film,the acid bath was transferred to the interior of a tubular dialysiscasing of regenerated cellulose and dialyzed by placing the acidbath-containing casing into a water filled vessel to which fresh waterwas continuously added. The dialysis was allowed to proceed for at least48 hours and the dialyzed regeneration bath was then removed from thecasing, concentrated by evaporation and analyzed by Infra-redspectroscopy to determine if any of the polymer additive PEO waspresent. This procedure was repeated for films made from viscosecontaining PEG and the results are summarized in Table 2 below.

                                      TABLE 2                                     __________________________________________________________________________         Type of                                                                            Weight Ratio                                                                           Weight of                                                                            Weight of                                                                           Polymer                                       Example                                                                            Polymer                                                                            of Cellulose to                                                                        Viscose &                                                                            Acid  Additive                                      No.  Additive                                                                           Polymer Additive                                                                       Additive (g)                                                                         Bath (g)                                                                            Detected by IR                                __________________________________________________________________________    3A   PEO* 83:17    105.9  500.0 NO                                            3B   PEG**                                                                              65:35     96.8  500.0 YES                                           3C   PEG**                                                                              98:2     303.0  1000.0                                                                              YES                                           __________________________________________________________________________     *Poly(ethylene oxide) commercially available from Union Carbide Corp.         under the trademark Polyox WSRN10 having a reported average molecular         weight of 100,000.                                                            **Polyethylene glycol commercially available from Union Carbide Corp.         under the trademark PEG 10000 having a reported average molecular weight      of 10,000.                                                               

The inclusion of poly(ethylene oxide) in the final film composite isfurther reinforced by laboratory work which show poly(ethylene glycol)present in the acid regeneration bath used to regenerate the viscose(having added PEG), whereas no poly(ethylene oxide) was detected in theacid regeneration bath used to regenerate those casings (having addedPEG).

Infra-red (IR) spectra were obtained for the dialyzed acid baths inExamples 3A-3C and compared to control samples which included solutionsof PEO dissolved in regeneration acid bath and PEG dissolved inregeneration acid bath. The PEO control comprised a 1.3% solution of PEOin bath, and the PEG control comprised a 3.3% solution of PEG in bath.These controls were similarly dialyzed and concentrated as describedabove for Examples 3A-3C prior to IR analysis. The dialyzing step wasperformed to remove the acid and sulfate components of the acid bathwhile retaining any PEG or PEO that had been washed out or leached outof the film into the bath during the coagulation/regeneration step. Alsocontrols of PEO in water and PEG in water were run at 8% (PEO) and at0.1%, 0.5%, 1%, 10%, and 20% (PEG). Comparison of the dialyzed,concentrated regeneration baths of Examples 3A-3C to the controlsclearly indicated that PEG which was added to the viscose washed out ofthe cellulose film. PEG residue was detected in the bath for filmshaving both high levels of addition (35% in Example 3B) and low levelsof addition (2% in Example 3C), whereas PEO was not detected in itsregeneration bath as seen in Example 3A (17% level of addition). Example3 further demonstrates that olefinic oxide polymers such aspoly(ethylene oxide) having a relatively high weight average molecularweight tend to remain incorporated in cellulose films formed fromextrudable cellulose or cellulose derivatives to which the polymer hasbeen added, while low molecular weight polymers such as polyethyleneglycol having a reported Mw of about 10,000 tend to leach or wash out ofthe film. This IR method of analysis is believed to be more accuratethan the calculated and measured weight method of the previous example.Preferably, films of the present invention will be substantially notleachable with greater than 98% of the olefin oxide polymer incorporatedand not easily washed out by contact with water or the typical aqueouswashing solution when applied to semifinished casing which haspreviously been dried down and then remoisturized as described above.

EXAMPLES 4-9

A series of seamless tubular cellulose films were produced via theviscose process described above. These films incorporated variousamounts of the polymer additives: poly(ethylene oxide) (PEO),poly(ethylene glycol) (PEG) and poly(ethyleneimine)(PEI) from solutionssimilar to B-G of Example 1. The tubular nonfibrous films designatedExamples 4-9 (Control and Samples A-C) were similarly made according toprocedures described above, but differed in the amount and type ofpolymer additive which was introduced prior to extrusion. Unless notedotherwise, the weight ratio of cellulose to additive was 99 to 1 basedupon Bone Dry Gauge for all of the Examples 4A-9A. Similarly Examples4B-9B had a weight ratio of 98 to 2 (BDG) and Examples 4C-6C had aweight ratio of 95 to 5. Unless otherwise noted for each example,control films were also made from the same viscose supply without anypolymer additive.

Film properties including burst pressure and diameter at burst weremeasured and results are reported in Tables 3A-3B.

For each example the same viscose supply was utilized for both thepolymer additive containing film and the control film which was madewithout any additive. The control films were plasticized by dipping inglycerine and were substantially similar to seamless, tubular,nonfibrous, regenerated cellulose casing used commercially in themanufacture of small diameter skinless sausages. The weight averagemolecular weight (Mw) of the cellulose in the films produced is believedto have been between about 95,000 to 120,000 and all of the filmsproduced are believed to have had a similar Mw. Molecular weightdistribution may be determined by the well known method of gelpermeation chromatography (GPC). Examples 4A and 5A are comparativeexamples (not of the invention).

The films were all extruded to a similar flatwidth between about 3-3.5cm. The values report in Table 3B for burst pressure and at burstdiameter are averages of two measurements.

                                      TABLE 3A                                    __________________________________________________________________________                 Film with Polymer Additive                                       Example                                                                            Control Film                                                                          Sol.                                                                             Additive                                                                            Molecular                                                                           Ratio Cellulose: Additive                         No.  Type    I.D.                                                                             Type  Weight                                                                              Sample A                                                                            Sample B                                                                            Sample C                              __________________________________________________________________________    4    100% Cellulose                                                                        E  PEG*    10,000                                                                            99:1  98:2  95:5                                  5    100% Cellulose                                                                        F  PEI**   50,000                                                                            99:1  98:2  95:5                                  6    100% Cellulose                                                                        B  PEO***                                                                                100,000                                                                           99:1  98:2  95:5                                  7    100% Cellulose                                                                        C  PEO****                                                                               900,000                                                                           99:1  98:2  --                                    8    100% Cellulose                                                                        D  PEO*****                                                                            4,000,000                                                                           99:1  98:2  --                                    9    100% Cellulose                                                                        D  PEO*****                                                                            4,000,000                                                                           ++    --    --                                    __________________________________________________________________________      Weight Average Molecular Weight (Mw)nominal value reported by                manufacturer.                                                                 *Polyethylene glycol commercially available from Union Carbide Corp. unde     the trademark PEG.                                                            **Polyethyleneimine commercially available from Cordova Chemical Company      under the trademark Corcat P600 having a reported average molecular weigh     range of 40,000-60,000.                                                       ***Poly(ethylene oxide) commercially available from Union Carbide Corp.       under the trademark Polyox WSRN10.                                            ****Poly(ethylene oxide) commercially available from Union Carbide Corp.      under the trademark Polyox WSR1105.                                           *****Poly(ethylene oxide) commercially available from Union Carbide Corp.     under the trademark Polyox WSR301.                                            ++Slightly more additive was present in this example and the ratio is         believed to be about 100:1.25.                                           

                  TABLE 3B                                                        ______________________________________                                        Example                                                                              Control    Sample A  Sample B                                                                              Sample C                                  No.    (100% Cell.)                                                                             (1% Add.) (2% Add.)                                                                             (5% Add.)                                 ______________________________________                                        Burst Pressure (mm Hg)                                                        4 (PEG)                                                                               356*      369       355     340                                       5 (PEI)                                                                               356*      351       346     329                                       6 (PEO)                                                                              348        359       363     349                                       7 (PEO)                                                                              350        343       362     --                                        8 (PEO)                                                                              350        --        350     --                                        9 (PEO)                                                                              349        367       --      --                                        ______________________________________                                        Casing Diameter at Burst (cm)                                                 4 (PEG)                                                                               3.9*      3.6       3.7     3.6                                       5 (PEI)                                                                               3.9*      3.9       3.6     3.6                                       6 (PEO)                                                                              3.8        3.9       3.8     3.8                                       7 (PEO)                                                                              3.7        3.3       3.7     --                                        8 (PEO)                                                                              3.5        --        3.6     --                                        9 (PEO)                                                                              3.8        3.5       --      --                                        ______________________________________                                         *Examples 4 and 5 utilized the same control sample.                      

The burst pressure and at burst diameter data in Table 3B indicate thatcellulose articles made according to the present invention have asufficient combination of strength and stretchability to withstand thepressures and internal forces encountered in stuffing and cookingoperations to be utilized as sausage casings. Examples 6-9 (all of theinvention) demonstrate that suitably strong films may be made over arange of levels of addition of poly(ethylene oxide) to cellulose andover a range of higher molecular weights. Films of the comparativeExamples 4 and 5 show a lowering of burst pressure at increasedconcentrations of lower molecular weight additives PEG and PEI incellulose. In contrast, when the higher molecular weight (100,000 andhigher) PEO is used casing strength is maintained.

The tubular cellulose film casings of Examples 4A-8A and 4B-8B wereshirred on apparatus and by a method similar to that disclosed in U.S.Pat. Nos. 2,984,574 and 4,578,842 into compressed sticks of casing usingprocedures similar to that for production of commercial shirred sticksof sausage casing. The shirred casing sticks of Examples 4, 5 and 8 allcontained about 160 linear feet (48.8 meters) of casing which wasshirred and compressed into sticks having the length indicated in Table4B. Examples 6, 7 and 9 are for shirred sticks containing about 210linear feet (64.0 meters). All of the casings of Examples 4-9 weresimilarly shirred using similar shirring parameters and equipment.

As each length of tubular cellulose casing was being shirred, a coatingcomposition (shirr spray) was applied by metering through the shirringmandrel along with a stream of inflation air. For Examples 4-9 theamount applied was about 3 mg of coating composition per square inch ofcasing (0.5 mg/cm²). The coating composition was a typical aqueousdispersion of a water-soluble cellulose ether (carboxymethyl cellulose),mineral oil, a surfactant (ethoxylated monodiglycerides) and a polyol(propylene glycol) such as disclosed in U.S. Pat. No. 4,596,727. Suchcomposition facilitates shirring and provides a coated casing suitablefor stuffing with meat emulsion on a high speed stuffing machine such asa Supermatic RT7 brand stuffer (available from Townsend EngineeringCompany of Des Moines, Iowa), and peeling on a high speed peeler such asa Ranger Apollo brand peeler (also available from Townsend EngineeringCompany). The resulting shirred coated casings had a moisture contentbetween about 25-32 percent. Also, the coating compositions for Examples4, 5, 7 and 8 contained about 18% of a polyol (propylene glycol) andapplication thereof to the casing is believed to have resulted in addingabout 2.8% by weight (BDG) of polyol to the casing. In Examples 6 and 9the coating composition contained a lesser amount of polyol (about 12%propylene glycol) which is believed to have resulted in adding about1.8% by weight (BDG) of polyol to the casing. For each example, equallengths of control casing and test casing were shirred into tubularsticks.

In general, no problems were encountered with shirring any of thepoly(ethylene oxide) containing casings. However, the comparativepoly(ethylene glycol) (PEG) and poly(ethylenimine) (PEI) casings weredifficult to shirr with examples 4A, 4B, 4C (PEG (MW=10,000)) and 5B, 5C(PEI (MW=40,000-60,000)) exhibiting excessive breakage during shirringand/or low water burst pressures when filled with water under pressure.The shirred casings were subjected to a series of stick propertyevaluations that are summarized below in Table 4A-4E.

                                      TABLE 4A                                    __________________________________________________________________________    Polymer    AVERAGE STICK WEIGHT (gm)                                          Example                                                                            Additive                                                                            CONTROL   SAMPLE A  SAMPLE B SAMPLE C                              No.  (Mol. Wt.)                                                                          Initial                                                                           7 Day Initial                                                                           7 Day Initial                                                                           7 Day                                                                              Initial                                                                           7 Day                             __________________________________________________________________________    4    PEG   141 141   124 121   125 124* 125 124                                    (10000)                                                                  5    PEI   141 141   125  125* 126  119**                                                                             125 125                                    (50000)                                                                  6    PEO   192   188***                                                                            169   168***                                                                            170  164***                                                                            167   166***                               (100000)                                                                 7    PEO   194 Nm    171 Nm    170 Nm   --  --                                     (900000)                                                                 8    PEO   141 139   126 126   124 124  --  --                                     (4000000)                                                                __________________________________________________________________________     Nm = Not measured                                                             *Measured 8 days after shirring.                                              **Measured 1 day after shirring (Sample weight measurements ranged from       109-125 grams. The standard deviation for other examples was typically        about 1 gram or less.).                                                       ***Measured 98 days after shirring.                                            Example 4 and 5 utilized the same control sample.                       

                                      TABLE 4B                                    __________________________________________________________________________    Polymer    AVERAGE STICK LENGTH (cm)                                          Example                                                                            Additive                                                                            CONTROL    SAMPLE A  A % DIFF.                                                                             SAMPLE B                              No.  (Mol. Wt.)                                                                          Initial                                                                            7 Day Initial                                                                           7 Day Initial                                                                           7 Day                                                                             Initial                                                                           7 Day                             __________________________________________________________________________    4    PEG   41.91+                                                                             43.15+                                                                              40.82                                                                             41.02 2.6%                                                                              4.9%                                                                              41.00                                                                             41.53*                                 (10000)                                                                  5    PEI   41.91+                                                                             43.15+                                                                              42.01                                                                             42.09*                                                                              -0.2%                                                                             2.5%                                                                              41.50                                                                             41.15**                                (50000)                                                                  6    PEO   54.74                                                                              55.65***                                                                            51.03                                                                               51.74***                                                                          6.8%                                                                              7.0%                                                                              50.75                                                                               50.77***                             (100000)                                                                 7    PEO   54.31                                                                              55.17 50.70                                                                             51.94 6.6%                                                                              5.9%                                                                              50.60                                                                             51.08                                  (900000)                                                                 8    PEO   42.11                                                                              42.75 40.06                                                                             40.39 7.7%                                                                              5.5%                                                                              39.57                                                                             39.37                                  (4000000)                                                                __________________________________________________________________________                      Polymer                                                                  Example                                                                            Additive                                                                            B % DIFF.                                                                             SAMPLE C  C % DIFF.                                        No.  (Mol. Wt.)                                                                          Initial                                                                           7 Day                                                                             Initial                                                                           7 Day Initial                                                                           7 Day                           __________________________________________________________________________                 4    PEG   2.2%                                                                              3.8%                                                                              40.41                                                                             40.69 3.6%                                                                              5.7%                                              (10000)                                                                  5    PEI   1.0%                                                                              4.6%                                                                              41.55                                                                             41.83 0.9%                                                                              3.1%                                              (50000)                                                                  6    PEO   7.3%                                                                              8.8%                                                                              49.94                                                                               50.47***                                                                          8.8%                                                                              9.3%                                              (100000)                                                                 7    PEO   6.8%                                                                              7.4%                                                                              --  --    --  --                                                (900000)                                                                 8    PEO   6.7%                                                                              7.9%                                                                              --  --    --  --                                                (4000000)                                                   __________________________________________________________________________     +Example 4 and 5 utilized the same control example.                           *Measured 8 days after shirring.                                              **Measured 1 day after shirring.                                              ***Measured 98 days after shirring.                                      

                                      TABLE 4C                                    __________________________________________________________________________    Polymer    HORN FIT (cm)                                                      Example                                                                            Additive                                                                            CONTROL    SAMPLE A  SAMPLE B                                                                              SAMPLE C                              No.  (Mol. Wt.)                                                                          Initial                                                                            7 Day Initial                                                                           7 Day Initial                                                                           7 Day                                                                             Initial                                                                           7 Day                             __________________________________________________________________________    4    PEG    1.35+                                                                             1.19+ 1.36                                                                              1.34  1.36                                                                               1.34*                                                                            1.37                                                                              1.35                                   (10000)                                                                  5    PEI    1.35+                                                                             1.19+ 1.36                                                                               1.30*                                                                              1.35                                                                               1.35**                                                                           1.35                                                                              1.32                                   (50000)                                                                  6    PEO   1.32 1.28***                                                                             1.36                                                                                1.30***                                                                           1.36                                                                                1.31***                                                                         1.36                                                                                1.33***                              (100000)                                                                 7    PEO   1.33 1.26  1.36                                                                              1.31  1.36                                                                              1.33                                                                              --  --                                     (900000)                                                                 8    PEO   1.35 1.29  1.35                                                                              1.35  1.37                                                                              1.35                                                                              --  --                                     (4000000)                                                                __________________________________________________________________________     +Example 4 and 5 utilized the same control example.                           *Measured 8 days after shirring.                                              **Measured 1 day after shirring.                                              ***Measured 98 days after shirring.                                      

                                      TABLE 4D                                    __________________________________________________________________________    Polymer    COHERENCY (cmKg)                                                   Example                                                                            Additive                                                                            CONTROL    SAMPLE A  SAMPLE B                                                                              SAMPLE C                              No.  (Mol. Wt.)                                                                          Initial                                                                            7 Day Initial                                                                           7 Day Initial                                                                           7 Day                                                                             Initial                                                                           7 Day                             __________________________________________________________________________    4    PEG   5.2+ 3.7+  8.3 5.6   8.3  9.0*                                                                             8.8 10.3                                   (10000)                                                                  5    PEI   5.2+ 3.7+  2.0  3.2* 3.2  4.2**                                                                            4.1 4.9                                    (50000)                                                                  6    PEO   2.6  4.4***                                                                              8.9   9.7***                                                                            9.8  11.3***                                                                          10.1                                                                               10.2***                               (100000)                                                                 7    PEO   3.4  4.3   9.7 6.6   6.1 10.0                                                                              --  --                                     (900000)                                                                 8    PEO   2.6  4.1   10.0                                                                              11.0  7.3 10.2                                                                              --  --                                     (4000000)                                                                __________________________________________________________________________     +Example 4 and 5 utilized the same control example.                           *Measured 8 days after shirring.                                              **Measured 1 day after shirring.                                              ***Measured 98 days after shirring.                                      

                                      TABLE 4E                                    __________________________________________________________________________    Polymer    DESHIRR FORCE (7 DAYS AFTER SHIRRING) (NEWTON)                     Example                                                                            Additive                                                                            CONTROL    SAMPLE A  SAMPLE B                                                                              SAMPLE C                              No.  (Mol. Wt.)                                                                          LOW  HIGH  LOW HIGH  LOW HIGH                                                                              LOW HIGH                              __________________________________________________________________________    4    PEG   1.535                                                                              2.127 1.687                                                                             2.488  1.887*                                                                            2.901*                                                                           1.633                                                                             2.336                                  (10000)                                                                  5    PEI   1.535                                                                              2.127  2.265*                                                                            3.271*                                                                              1.526**                                                                           2.207**                                                                          1.513                                                                             2.225                                  (50000)                                                                    6***                                                                             PEO   1.949                                                                              3.204 2.060                                                                             3.662 2.092                                                                             3.458                                                                             2.060                                                                             3.729                                  (100000)                                                                 7    PEO   2.065                                                                              3.204 2.221                                                                             3.475 2.287                                                                             3.324                                                                             --  --                                     (900000)                                                                 8    PEO   1.406                                                                              2.127 1.598                                                                             2.198 1.558                                                                             2.189                                                                             --  --                                     (4000000)                                                                __________________________________________________________________________      Example 4 and 5 utilized the same control example.                           *Measured 8 days after shirring.                                              **Measured 1 day after shirring.                                              ***All samples in Example 6 were measured 98 days after shirring.        

The test results show all of the casings to have reduced stick weightsof about 9-16% relative to the control samples. Examples 6A-8A and 6B-8Bof the invention were poly(ethylene oxide) containing casings which showreduced stick lengths of about 6-9% and increased coherency valuesrelative to control samples without undesirably large increases indeshirr forces. Comparative Examples 4A, 4B and 4C (PEG) showed someimprovement in reducing stick length (2-6%) and coherency but not thedramatic improvements shown by the inventive casings. ComparativeExamples 5A, 5B and 5C (PEI) show little or no improvement in sticklength or coherency values. Also as noted above, the comparativeExamples 4 and 5, particularly at higher additive concentrations tendedto exhibit unacceptable breakage i.e. splitting and bursting of thecasing wall during the shirring process. The casings of Examples 4 and 5also tended to show unacceptably low water burst pressures which isindicative of a casing having insufficient resistance to bursting whenfilled e.g. with a wet food emulsion during a typical stuffingoperation. The casings of the invention shirred as well as the controlcasing. The horn fit values of all the test casings exhibited excellentstability over time relative to the control samples. There was littlereduction in the bore diameters measured after 7 days from the initialvalues measured soon after shirring. Shirring conditions were similarfrom example to example and no attempt was made to maximize the borediameter of any particular casing. However, it is believed that theshorter shirred stick lengths for equal lengths of casing (which is alsoindicative of a higher pack ratio for the inventive casings which haveincreased bore diameters relative to the controls) suggest that shirredsticks may be produced with the inventive casings which have increasedbore diameters relative to present commercial casings having a shirredstick length equal to that of the inventive casing.

The decreased stick lengths and weights are believed to be due to theabsence of glycerine in the test casings relative to the control casingswhich were dipped in glycerine as is conventional to plasticize andsoften the casing to prevent breakage during reeling, shirring and use.It is believed that all presently commercialized tubular, nonfibrousshirred cellulose sausage casings utilize added polyols such asglycerine to prevent breakage. The present invention is believed toproduce for the first time a commercially acceptable shirred tubularcellulose casing having less than 5% (BDG) of any post-extrusion addedsoftener or plasticizer (except for water) and makes possible theproduction of casings suitable for commercial high speed stuffing andpeeling operations and having less than 5% of a polyol such glycerine,preferably less than 3% and beneficially substantially polyol freecasing.

Shirred sticks of casings made according to Examples 4, 5, 8 and 9 abovewere conventionally stuffed to a typical recommended average stuffingdiameter of about 23 mm for a nominal 3.3 cm flatwidth casing. For eachexample, control casings and test casings containing a peelability andshirring enhancing coating composition were similarly stuffed with acommercially available high collagen ground meat (beef and pork)emulsion. Stuffing was performed on a commercially available SuperMAticRT-7 brand frankfurter stuffing machine manufactured by TownsendEngineering Co. of Des Moines, Iowa. The meat emulsion utilized andequipment set up and processing conditions and parameters were similarfor all examples and controls. A 14/32 inch (1.11 cm) diameter stuffinghorn was utilized and the pump speed was set at about 499 rpm. Stuffingbreakage data are reported in Table 5A. Two separate tests wereconducted of comparative Examples 4 and 5 and the stuffing breakageresults are reported as examples 4i, 4ii, 5i and 5ii. Also, shirredsticks of casings made according to Examples 4, 5 and 9 above weresimilarly stuffed but to an average stuffed diameter of about 24 mm byadjusting (lowering) the linker speed of the stuffing machine. Otherparameters were held constant. Stuffing breakage data for the 24 mmstuffed diameter casings and are reported in Table 5B below.

                                      TABLE 5A                                    __________________________________________________________________________          # of  STUFFING BREAKAGE                                                 Example                                                                             SHIRRED                                                                             (#/TYPE)* AT AVG. STUFFED DIAMETER (mm)                           No.   STICKS                                                                              CONTROL                                                                              SAMPLE A                                                                             SAMPLE B                                                                              SAMPLE C                                    __________________________________________________________________________    4i (PEG)                                                                            2     1/1B   8/5B, 3T                                                                             7/3B, 4T                                                                              1/1B                                                    (23 mm)                                                                              (23 mm)                                                                              (23 mm) (23 mm)                                     4ii (PEG)                                                                            11/2 NONE   3/2B, 1PH                                                                            2/2B    NONE                                                    (23 mm)                                                                              (23 mm)                                                                              (23 mm) (23 mm)                                     5i (PEI)                                                                            2     1/1T   NONE   2/1B, 1T                                                                              21/17B, 2T, 1PH, 1S                                     (23 mm)                                                                              (23 mm)                                                                              (23 mm) (22 mm)                                     5ii (PEI)                                                                            11/2 NONE   9/9B   14/14B  --                                                      (23 mm)                                                                              (23 mm)                                                                              (23 mm)                                             8 (PEO)                                                                             3     NONE   1/1B   6/4B, 1T, 1S                                                                          --                                                      (23 mm)                                                                              (23 mm)                                                                              (23 mm)                                             9 (PEO)                                                                             3     NONE   NONE   --      --                                                      (23 mm)                                                                              (23 mm)                                                    __________________________________________________________________________     *Casing Breakage: B = Body; T = Twist; PH = Pinhole; S = Shoulder        

                                      TABLE 5B                                    __________________________________________________________________________          # of  STUFFING BREAKAGE                                                 Example                                                                             SHIRRED                                                                             (#/TYPE)* AT AVG. STUFFED DIAMETER (mm)                           No.   STICKS                                                                              CONTROL                                                                              SAMPLE A                                                                             SAMPLE B                                                                              SAMPLE C                                    __________________________________________________________________________    4 (PEG)                                                                             5     NONE   10/7B, 3T                                                                            5/3B, 2T                                                                              1/1T                                                    (24 mm)                                                                              (24 mm)                                                                              (24 mm) (24 mm)                                     5 (PEI)                                                                             5     NONE   5/4B, 1T                                                                             15/10B, 3T,                                                                           50/45B, 5T                                              (24 mm)                                                                              (24 mm)                                                                              1PH, 1S (24 mm)                                                               (24 mm)                                             9 (PEO)                                                                             3     3/1T, 2S                                                                             NONE   --      --                                                      (24 mm)                                                                              (24 mm)                                                    __________________________________________________________________________     *Casing Breakage: B = Body; T = Twist; PH = Pinhole; S = Shoulder        

The PEI containing casing exhibited high levels of breakage at bothstuffing diameters particularly for casings containing higher amounts ofPEI. The PEG containing casings also exhibited a high level of breakageat the 1% and 2% additive levels. The inventive casing containing PEOgenerally exhibited little or no stuffing breakage particularly at lowlevels of added polymer additive.

EXAMPLES 10-18

Tubular seamless cellulose casing was made by a method similar to thatdescribed above. An olefinic oxide polymer (POLYOX WSR-301) was added tothe viscose prior to extrusion to produce regenerated cellulose havingpoly(ethylene oxide) in the amount of 1% (BDG) for Examples 11, 13, 15and 17 and in the amount of 2% (BDG) for Examples 12, 14, 16 and 18.Control Example 10 was 100% cellulose (BDG) having no added polymer. Incontrol Example 10, the casing following regeneration and washing wasdipped into a softener/plasticizer (glycerine) by passing the casinginto and out of a tub of an aqueous solution of about 5-10% glycerinethree times. In Examples 11-18 (all of the invention) the number of dips(which is proportional to the contact time of the casing with glycerine)were varied from 0 to 3 for the examples as indicated in Table 6. Theamount of glycerine taken up (incorporated in and coated on) by thecasing is reported as a weight percent based on BDG. Equal lengths(about 160 feet (48.8 meters)) of casings were similarly shirred intotubular sticks as described in the above examples and the shirred sticklengths (average of 5) and coherency values (average of 5) were measuredinitially the same day shirred and after 7 days and these data arereported in Table 6 below.

                                      TABLE 6                                     __________________________________________________________________________                          Amt.                                                              Ratio of                                                                            Glycerine                                                                           Glycerine                                                                             Stick   Coherency                               Example                                                                            Polymer                                                                            Cellulose                                                                           DIPS  on Casing                                                                             Length (cm)                                                                           (cmKg)                                  No.  Additive                                                                           to Additive                                                                         #     Wt. % (BDG)                                                                           Initial                                                                           7 Days                                                                            Initial                                                                           7 Days                              __________________________________________________________________________    10   None --    3     14.2    42.3                                                                              42.7                                                                              5.3 4.1                                 11   PEO* 99:1  3     17.2    41.9                                                                              42.4                                                                              5.9 7.3                                 12   PEO* 98:2  3     17.1    41.6                                                                              42.6                                                                              6.1 6.7                                 13   PEO* 99:1  2     13.0    40.6                                                                              41.8                                                                              7.7 7.5                                 14   PEO* 98:2  2     14.0    41.0                                                                              41.3                                                                              7.3 9.2                                 15   PEO* 99:1  1     7.8     40.6                                                                              40.8                                                                              9.1 10.4                                16   PEO* 98:2  1     8.0     40.3                                                                              40.8                                                                              6.1 9.0                                 17   PEO* 99:1  0     0.3     40.1                                                                              40.4                                                                              9.1 11.0                                18   PEO* 99:2  0     0.4     39.5                                                                              39.4                                                                              7.6 10.2                                __________________________________________________________________________     *Poly(ethylene oxide) commercially available from Union Carbide Corp.         under the trademark POLYOX WSR301 having a reported nominal average           molecular weight of 4,000,000.                                           

The data presented in Table 6 demonstrates that reducing or eliminatingthe addition of plasticizers such as glycerine results in shorter sticklengths for an equal amount of shirred casing relative to casing havingadded glycerine. The achievable packing efficiency is increased, whichis desirable. This allows improved product attributes of eitherincreased bore or increased pack ratio or a combination thereof. Thedata also indicate that glycerine is taken up faster by the inventivecasing and that two dips with the inventive casing will take up aboutthe same amount of glycerine plasticizer as three dips with the 100%cellulose control.

Thus the contact time of the inventive casing with the plasticizer maybe reduced (by about 33% for Example 14) without reducing the level ofadded glycerine plasticizer. All examples of the invention exhibitexcellent stick coherency values.

Reduction of stick lengths permits multiple sticks of shirred casing tobe transported in smaller packages. It should also be apparent from thisand the previous Examples 4-9 that reducing or eliminating plasticizerssuch as glycerine reduces the weight of each stick of casing therebyreducing shipping/transportation costs.

Comparison of initial average stick length values with those measuredafter seven days indicates that shirred sticks tend to have more stable(less change) lengths with decreasing glycerine content.

EXAMPLE 19-25

A cellulose article comprising fiber-reinforced (fibrous) tubularcellulose casing suitable for stuffing with a foodstuff such as meat wasprepared by conventional apparatus and procedures. A commerciallyavailable paper web made and sold for use in the production ofcommercial fiber-reinforced casing was folded into a tube and theoutside of the tube was coated with viscose as described above in amanner conventional in the art. As known in the art, the paper tubefunctions as the fiber-reinforcement and the applied viscose penetratesinto the paper. The paper web may also be coated with viscose from theinterior or from both sides of the paper. A control Example 19 (not ofthe invention) was made which did not contain any olefinic oxidepolymer. In Examples 20-25, a 15% aqueous solution of olefinic oxidepolymer comprising poly(ethylene oxide) (commercially available asPOLYOX WSRN-10, as described above from Union Carbide Corp.) wasuniformly mixed with a reduced viscose flow to produce a coatingmaterial which after regeneration had a cellulose to poly(ethyleneoxide) weight ratio as indicated in the Table 7A. This solution wassimilarly prepared as for solution A of Example I. The poly(ethyleneoxide) solution was added to viscose via a pigmentor normally used toadd colorant to viscose in fibrous casing manufacture. The viscose wascoated on a paper tube which then passed through acoagulation/regeneration bath typical of that utilized in fibroussausage casing manufacture. After typical neutralization and washingsteps, the casings of Examples 19, 20, 22 and 24 were passed through atub containing about 10 weight percent glycerine in water. The casingsof Examples 21, 23 and 25 omitted passage through the glycerinecontaining tubs. All of the casings of Examples 19-25 were theninternally treated by slugging with a dry sausage treatment comprisingan aqueous solution of about 1.2% of a polyamide-epichlorohydrin resinsuch as that commercially available under the treatment Kymene 4190 fromHercules Incorporated of Wilmington, Del., and about 5.8% glycerine. Thetreated casings were conventionally dried to a moisture level of about6-10% based upon the Bone Dry Gauge weight and wound on reels. The wetthickness, flatwidth, bone dry gauge, polyol content, average wetmullens strength, at burst diameter, burst pressure and ultrafiltrationwere all measured and values reported in Table 7A below along with thecircumferential burst stress which is calculated using the well knownformula: ##EQU3## The reported values for Bone Dry Gauge (BDG), At BurstDiameter, Burst Pressure, and flatwidth are averages of two measurementsand the wet thickness is an average of 5 measurements.

Prior to shirring, the reeled fibrous casing was unreeled and sprayedwith about an 18% propylene glycol in water solution and rereeled. Thecasings were weighed before and after spraying and the added moisture isreported in Table 7B as weight percent relative to the weight of thecasing prior to this spraying step. The rereeled casings were thensimilarly shirred into compressed sticks containing 120 foot (36.6meter) lengths of casing. The lengths of the shirred sticks weremeasured and the weight measurement for two sticks (three for thecontrol Example 19) are reported in Table 7B. Shirred stick length wasmeasured initially on the same day shirred and then again twelve daysafter shirring. Test results are reported below in Tables 7A and 7B.

                                      TABLE 7A                                    __________________________________________________________________________         Weight Ratio*      Bone Amount                                                                             Wet     At                                       in Coating                                                                            Wet   Flat-                                                                              Dry  of Polyol                                                                          Mullens Burst                                                                              Burst                                                                              Burst                     Example                                                                            of Cellulose                                                                          Thickness                                                                           width                                                                              Gauge                                                                              in Casing                                                                          Burst   Diameter                                                                           Pressure                                                                           Stress                    No.  to PEO  (micron)                                                                            (cm) (mg/cm)                                                                            (wt %)                                                                             Strength (kPa)                                                                        (cm) (mmHg)                                                                             MPa                       __________________________________________________________________________    19   --**    115   6.18 73   24.7 276     4.79 810  45                        20   98:2    110   6.26 74   24.2 252     4.76 801  46                        21   98:2    107   6.29 81   1.5  299     4.79 941  56                        22   95:5    112   6.30 73   20.0 241     4.76 786  45                        23   95:5    100   6.45 72   3.6  252     4.76 836  53                        24   93:7    111   6.25 71   21.1 226     4.76 793  45                        25   93:7    106   6.24 71   0.8  217     4.75 797  48                        __________________________________________________________________________     *Ratio is for coating only and does not include cellulose of the paper        web.                                                                          **No PEO was added in this control example (not of the invention).       

                  TABLE 7B                                                        ______________________________________                                        Ultra-                                                                        Filtration   Added    Average Shirred Stick Length)                           Example                                                                              (Δ v/min.                                                                         Moisture Initial                                                                             12 Days                                       No.    M.sup.2 mmHg)                                                                           wt. %    (cm)  (cm)   % Change                               ______________________________________                                        19     1.25      31.6     41.9  43.7   +4.3                                   20     .86       28.3     40.7  41.9   +2.9                                   21     .54       27.7     40.6  40.6   0                                      22     1.01      30.5     40.6  41.3   +1.6                                   23     .64       33.7     40.3  40.3   0                                      24     .87       29.0     40.6  41.4   +2.1                                   25     .53       33.3     40.0  40.0   0                                      ______________________________________                                    

The data in Tables 7A-7B demonstrate that fibrous casing articles madewith a coating having reduced cellulose and containing an olefin oxidepolymer such as poly(ethylene oxide) have sufficient wet strength, burstpressure, and at burst diameter and circumferential burst stress valuesto indicate an ability to withstand the pressures and stressesencountered in stuffing casings with meat emulsion. The circumferentialburst stress values indicate that the inventive casings of Examples 21,23 and 25, which omitted the polyol tub dips were able to withstandsignificantly higher circumferential stresses before rupture. Reducedultrafiltration values are reported for the inventive casings relativeto the control. However, it is believed that the permeability of theinventive casing as indicated by the reported values is sufficient foruse as sausage casings and may provide an advantage for separatorymembrane applications requiring modified ultrafiltration rates. Theshirring data indicate an important advantage in that equal lengths ofcasings may under the same conditions be shirred to shorter sticklengths. In particular, the glycerine dip may be omitted, which forExamples 21, 23 and 25 demonstrate remarkable shirred stick lengthstability relative to the glycerinated control Example 19 (not of theinvention).

EXAMPLES 26-29

A series of seamless tubular cellulose films were produced via theviscose process described above. The tubular nonfibrous films designatedExamples 26-29 were similarly made according to procedures describedabove, but differed in whether glycerine was added and in the amount andtype of olefin oxide polymer additive (PEO) which was introduced priorto extrusion. The weight ratio of cellulose to additive was 98 to 2based upon Bone Dry Gauge for Examples 28 and 29 of the invention.Example 28 was a cellulosic casing containing a 100,000 Mw poly(ethyleneoxide) polymeric additive at a level of about 2% by weight BDG which wasincorporated using a solution similar to that described above in Example1 as Solution B. Similarly, Example 29 utilized a solution similar tothat of Solution G of Example 1 to incorporate about 2% (BDG) of4,000,000 Mw PEO into a cellulosic casing. Two control films (Examples26 and 27) were also made from the same viscose supply without anypolymer additive.

Film properties including burst pressure and diameter at burst weremeasured and results are reported in Tables 8A-8C.

For each example the same viscose supply was utilized for both thepolymer additive containing film and the control films 26 and 27 whichwere made without any additive. Control film 26 was plasticized bydipping in glycerine and was substantially similar to seamless, tubular,nonfibrous, regenerated cellulose casing used commercially in themanufacture of small diameter skinless sausages. A second control film27 was similar to the first control film 26, but omitted addition of anyglycerine. The weight average molecular weight (Mw) of the cellulose inthe films produced is believed to have been between about 95,000 to120,000 and all of the films produced are believed to have had a similarMw. Molecular weight distribution may be determined by the well knownmethod of gel permeation chromatography (GPC). Examples 26 and 27 arecomparative examples (not of the invention).

The films were all extruded to a similar flatwidth of about 3-3.5 cm.The values report in Table 8A for burst pressure and at burst diameterare averages of two measurements. The reported "dry" thickness value isan average of four measurements of the reel stock casing after dryingand with moisture control, but prior to any shirring. All casings testedwere moisturized after drying to level of about 11-16% BDG. The reported"wet" thickness values for control films 26 and 27 are an average offive measurements of sample film from four reels (20 measurements)whereas the wet thickness values for Examples 28 and 29 of the inventionare averages of five measurements of sample film from ten reels ofcasing (50 measurements). The wet thickness measurements were of casingsamples which were similarly soaked in water for at least 30 minutes.The circumferential burst stress was calculated according to the formuladescribed above with respect to Examples 19-25, utilizing the averagewet thickness values. Wet values are used to calculate burst stressvalues for conditions similar to those found in commercial practicewhere the tubular films are or become wet during stuffing operations.

                                      TABLE 8A                                    __________________________________________________________________________          Ratio of                                                                      Cellulose    Dry   Wet   Burst                                                                              At Burst                                                                           Burst                                      to Polyox in Thickness                                                                           Thickness                                                                           Pressure                                                                           Diameter                                                                           Stress                               Example #                                                                           the Final Film                                                                        Glycerin                                                                           (micron)                                                                            (micron)                                                                            (mmHg)                                                                             (cm) (MPa)                                __________________________________________________________________________    26    100:0   Yes  26    56.3  315  3.99 30                                   27    100:0   No   20    53.0  332  3.78 32                                   28    98:2*   No   21    52.1  324  3.49 29                                   29     98:2** No   22    50.4  319  3.87 33                                   __________________________________________________________________________     *Poly(ethylene oxide) commercially available from Union Carbide Corp.         under the trademark Polyox WSRN10.                                            **Poly(ethylene oxide) commercially available from Union Carbide Corp.        under the trademark Polyox WSR301.                                       

The burst pressure, at burst diameter, and circumferential burst stressdata in Table 8A indicate that cellulose articles made according to thepresent invention have a sufficient combination of strength andstretchability to withstand the pressures and internal forcesencountered in stuffing and cooking operations to be utilized as sausagecasings.

The tubular cellulose film casings of Examples 26-29 were shirred onapparatus and by a method similar to that disclosed in U.S. Pat. Nos.2,984,574 and 4,578,842 into compressed sticks of casing usingprocedures similar to that for production of commercial shirred sticksof sausage casing. The shirred casing sticks of Examples 26-29 allcontained about 110 linear feet (33.3 meters) of casing which wasshirred and compressed into sticks having the lengths indicated in Table8B. All of the casings were similarly shirred.

As each length of tubular cellulose casing was being shirred, a coatingcomposition (shirr spray) was applied by metering through the shirringmandrel along with a stream of inflation air as described above forExamples 4-9.

The resulting shirred coated casings had a moisture content betweenabout 30-36 percent. Also, the coating compositions contained about 18%of a polyol(propylene glycol) which is believed to have resulted inadding about 2.8% by weight (BDG) of polyol to the casing (BDG). Thispolyol acts as an antimycotic, humectant and plasticizer. For eachexample, equal lengths control casing and test casing were shirred intotubular sticks.

In general, no problems were encountered with shirring any of thecasings. Generally, casings of lengths less than 160 feet are relativelyeasy to shirr, but shirring conventional casings of lengths of 190 feetor more generally require application of substantial forces which tendto result in shirring problems and higher levels of defective shirredcasing having pinholes and other shirring related weaknesses which makethe casings susceptible to failure during stuffing. The shirred casingswere subjected to a series of stick property evaluations that aresummarized below in Table 8B.

                                      TABLE 8B                                    __________________________________________________________________________    Ratio of           Stick                                                      Cellulose          Weight                                                                              Stick Length                                                                            Coherency                                                                              Horn Fit                          to Polyox in       (g)   (cm)      (cmKg)   (cm)                              Example #                                                                           the Final Film                                                                        Glycerin                                                                           5 Days                                                                              Initial                                                                           5 Days                                                                              Initial                                                                           5 Days                                                                             Initial                                                                           5 Days                        __________________________________________________________________________    26    100:0   Yes  98.5  38.74                                                                             38.81 4.1 7.1  1.372                                                                             1.346                         27    100:0   No   88.2  38.43                                                                             38.86 4.6 7.4  1.361                                                                             1.328                         28    98:2*   No     90.1***                                                                           38.10                                                                               38.73***                                                                          4.3   7.6***                                                                           1.392                                                                               1.346***                    29     98:2** No   87.9  38.10                                                                             38.56 5.5 6.8  1.397                                                                             1.346                         __________________________________________________________________________     *Poly(ethylene oxide) commercially available from Union Carbide Corp.         under the trademark Polyox WSRN10.                                            **Poly(ethylene oxide) commercially available from Union Carbide Corp.        under the trademark Polyox WSR301.                                            ***Measured 3 days after shirring.                                       

The test results show all of the nonglycerinated casings to have reducedstick weights of about 9-11% relative to the glycerated control Example26. Examples 28 and 29 of the invention were poly(ethylene oxide)containing casings which show slightly reduced stick lengths and similarcoherency and horn fit values relative to the control example. Shirringconditions were similar from example to example and no attempt was madeto maximize the pack ratio or bore diameter of any particular casing.These Examples 26-29 show that shorter lengths of the casing may beshirred at lower pack ratios with casings of the present invention ascompared to the more difficult to shirr longer lengths and higher packratio shirred sticks such as those disclosed in Examples 4-9. Thedramatic improvements in shirring related properties of the presentinvention are more readily apparent for shirred sticks having high packratios.

The above shirred sticks of casings of Examples 26-29 to Examples 4 wereconventionally stuffed to a typical recommended average stuffingdiameter of about 23 mm for a nominal 3.3 cm flatwidth casing. For eachexample, control casings and test casings containing a peelability andshirring enhancing coating composition were similarly stuffed with acommercially available frankfurter meat emulsion. Stuffing was performedon a commercially available Supermatic RT-7 brand frankfurter stuffingmachine manufactured by Townsend Engineering Co. of Des Moines, Iowa.The meat emulsion utilized and equipment set up and processingconditions and parameters were similar for all examples and controls.

A second stuffing test was conducted similar to that above, except thatthe casings were stuffed to larger stuffing diameter in order to testthe casings under more stressful conditions. These casings were stuffedwith a gelled polyacrylamide resin which was used as a meat emulsionsubstitute for test purposes. The stuffing breakage results andmeasurements of various properties are reported in Table 8C.

                                      TABLE 8C                                    __________________________________________________________________________                       Test 1           Test 2                                          Ratio of          Measured          Measured                                  Cellulose    # Of Stuff Stuffing                                                                            # Of  Stuff Stuffing                            to Polyox in Sticks                                                                             Diameter                                                                            Breakage                                                                            Sticks                                                                              Diameter                                                                            Breakage                      Example #                                                                           the Final Film                                                                        Glycerin                                                                           Stuffed*                                                                           (mm)  (#/Type)+                                                                           Stuffed**                                                                           (mm)  (#/Type)+                     __________________________________________________________________________    26    100:0   Yes  3    22.91 None  10    24.5  None                          27    100:0   No   3    23.00 None  10    24.5  4/2T, 2B                      28    98:2++  No   3    23.00 None  10    24.5  2/1B, 1PH                     29    98:2+++ No   3    22.97 None  10    24.5  3/2T, 1B                      __________________________________________________________________________     *Casings stuffed with commercially available hot dog emulsion                 **Casings stuffed with a polyacrylamide resin sold under the trade name       TERRASORB by Industrial Services International, Inc. as a hot dog emulsio     substitute.                                                                   +Casing breakage = B = Body, T = Twist, P = Pinhole, S = Shoulder             ++Poly(ethylene oxide) commercially available from Union Carbide Corp.        under the trademark Polyox WSRN10.                                            +++Poly(ethylene oxide) commercially available from Union Carbide Corp.       under the trademark Polyox WSR301.                                       

All of the casings of Examples 26-29 stuffed well, without any breakage,to the recommended stuffing diameter of about 23 mm. The repeated testusing a meat emulsion substitute to overstuff to a stuffing diameter of24.5 mm resulted in breakage of the unglycerinated casings. The 100,000Mw PEO containing casing of Example 28 had half the number of breaks ofthe unglycerinated control Example 27. The 4,000,000 Mw PEO containingcasing of Example 29 had one fewer break (2 versus 3) relative tounglycerinated control Example 27. These examples indicated thatunglycerinated tubular cellulosic films containing an olefinic oxidepolymer according to the present invention are less susceptable tostuffing breakage than unglycerinated cellulose casings made without anypolymer additive.

A third stuffing test was conducted similar to the above tests oncasings 26a, 27a and 28a which were from the same batch of casings asExamples 26-28, but aged for about one year. These casings of Examples26a-28a and a fresh glycerinated control casing were similarly stuffedas above except that a gelled polyacrylamide resin was used as a meatemulsion substitute for test purposes and the stuffing diameter wasabout 23.5 mm. The stuffing breakage results test data are reported inTable 8D below.

                                      TABLE 8D                                    __________________________________________________________________________                       Test 1                                                           Ratio of          Measured                                                    Cellulose    # Of Stuff Stuffing                                              to Polyox in Sticks                                                                             Diameter                                                                            Breakage                                        Example #                                                                           the Final Film                                                                        Glycerin                                                                           Stuffed*                                                                           (mm)  (#/Type)+                                       __________________________________________________________________________    Fresh 100:0   Yes  7    23.5  1/1B                                            Control                                                                       26a   100:0   Yes  7    23.5  1/1B                                            27a   100:0   No   15   23.5  3/3B                                            28a      98:2++                                                                             No   7    23.5  0                                               __________________________________________________________________________     *Casings stuffed with a polyacrylamide resin sold under the trade name        TERRASORB by Industrial Services International, Inc. as a hot dog emulsio     substitute.                                                                   +Casing breakage = B = Body, T = Twist, P = Pinhole, S = Shoulder             ++Poly(ethylene oxide) commercially available from Union Carbide Corp.        under the trademark Polyox WSRN10.                                            +++First two breaks occurred in first seven sticks tested.               

The "fresh control" casing was a glycerinated commercial nonfibrouscasing which was similar to Example 26a except that the shirringoperation was conducted differently to obtain a length of 210 feet pershirred stick. This control was used to determine that the stuffingequipment was functioning properly. One break occurred in seven sticksof casing as it was stuffed. The one year old control casing of Example26a also exhibited one break. The olefin oxide polymer free control(Example 27) which also did not have any added glycerine (but did havepropylene glycol added during shirring) experienced two breaks in thefirst seven sticks stuffed. An additional eight sticks of the casing ofExample 27a were stuffed and one additional break was noted. Sevensticks of the one year old casing of the invention (Example 28a) werestuffed without any breakage.

It is known that over time, cellulose casing tends to dry out, becomesmore brittle and is subject to increased rates of breakage when handledor used e.g. as sausage casing unless it is sufficiently plasticized,typically with glycerine (which is a hygroscopic material). Regardingthe present invention, it is believed that olefinic oxide polymers suchas poly(ethylene oxide) obviate the need for polyols such as glycerineby replacing their plasticizing function. Cellulose casing containingpoly(ethylene oxide) according to the present invention which has beenaged for about one year after shirring has been stuffed and found to benot brittle. Instead, these aged casings of the invention remainsufficiently flexible and suitable to be stuffed and generally used asfood casings e.g. for processing sausages such as skinless frankfurters.In contrast, similarly aged unglycerinated casings which aresubstantially pure regenerated cellulose not containing any added olefinoxide polymer such as poly(ethylene oxide) had an unduly high breakagerate during stuffing as seen above in Table 8D.

EXAMPLES 30-32

A series of seamless tubular cellulose films were produced via theviscose process described above. The tubular nonfibrous films designatedExamples 30-32 were similarly made according to procedures describedabove, but differed in whether glycerine was added and in the amount ofolefin oxide polymer additive (PEO) which was introduced prior toextrusion. Example 30 was a control film (not of the invention which wasglycerinated by passing through 3 dip tubs and which did not contain anyadded olefin oxide polymer. Examples 31 and 32 were cellulose casingscontaining a 100,000 M_(w) poly(ethylene oxide) polymer additive at alevel of about 1% (Example 31) and 2% (Example 32) by weight BDG whichwas incorporated using a solution similar to that described above inExample 1 as Solution B. The casings of the inventive Examples 31 and 32were unglycerinated. Casings of all three examples were similarlyshirred in lengths of 230 feet (70.1 meters) using the same type ofcoatings during shirring. Stick weight, horn fit, stick length andcoherency properties of the shirred sticks were measured and arereported below in Table 9.

                                      TABLE 9                                     __________________________________________________________________________    LONG LENGTH SHIRRING                                                          __________________________________________________________________________           RATIO OF                                                                      CELLULOSE TO                                                           EXAMPLE                                                                              POLYOX WSRN-10 IN                                                                         STICK WT. (gms)  HORN FIT (cm)                             NO.    THE FINAL FILM                                                                            INITIAL                                                                             7 DAYS                                                                             60 DAYS                                                                             INITIAL                                                                             7 DAYS                                                                             60 DAYS                        __________________________________________________________________________    30     100:0       208   208  205   1.295 1.270                                                                              1.267                          31     99:1        184   184  182   1.323 1.308                                                                              1.306                          32     98:2        182   182  180   1.318 1.318                                                                              1.303                          __________________________________________________________________________           RATIO OF                                                                      CELLULOSE TO                                                           EXAMPLE                                                                              POLYOX WSRN-10 IN                                                                         STICK LENGTH (cm)                                                                              COHERENCY (cmKg)                          NO     THE FINAL FILM                                                                            INITIAL                                                                             7 DAYS                                                                             60 DAYS                                                                             INITIAL                                                                             7 DAYS                                                                             60 DAYS                        __________________________________________________________________________    30     100:0       55.67 55.70                                                                              55.52 4.20  5.04 6.96                           31     99:1        52.98 53.06                                                                              52.93 5.64  6.00 5.76                           32     98:2        51.97 51.97                                                                              52.10 9.70  10.44                                                                              11.04                          __________________________________________________________________________

The results of the tests in Table 9 indicate that same lengths of theinventive casings may be shirred and compacted under the same conditionsto shorter lengths of shirred sticks having less weight and larger hornfit sizes than prior art casing. The coherency values of the inventivecasings are generally as good or much better than the control example.

Thus, equal lengths of the inventive casing may be shipped in lighterpackages. Also, the inventive shirred sticks may be used on stuffingmachines with larger diameter stuffing horns allowing faster productionby increasing sausage throughput during stuffing without causing adeleterious loss of particle definition or emulsion break down. Theinvention allows the flexibility to change horn fit sizes or pack ratiosto maximize the length of casing in a predetermined size stick length ormaximize stuffing throughput or to have a better combination of horn fitand pack ratio relative to the prior art. Also, less work is required tosimilarly shirr the inventive casings to predetermined specifications oflength, horn fit, pack ratio compared to prior art casings.Additionally, shirred waste due to pinhole defects and other shirringrelated terms is reduced.

The pack ratio for Example 32 was determined to be 8% higher than thecontrol (Example 30) even though the packing efficiency for Example 32was slightly lower than that for Example 30 (56.5% and 57.9%respectively). This means that the inventive casings produce anincreased latitude in controlling shirring variables. In other words, ifcasing of the invention is packed to the same packing efficiency as theprior art casing, then the inventive casing will have a bettercombination of horn fit and pack ratio.

As mentioned before, the above examples serve only to illustrate theinvention and its advantages, and they should not be interpreted aslimiting since further modifications of the disclosed invention will beapparent to those skilled in the art. All such modifications are deemedto be within the scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A cellulosic tubular food casing containing anolefinic oxide polymer uniformly dispersed through the tube wall inadmixture with the cellulose and in sufficient quantity so that theolefinic oxide polymer-to-cellulose weight ratio is at least about1:200, and wherein said olefinic oxide polymer has an average molecularweight of at least about 70,000.
 2. An article according to claim 1wherein said olefinic oxide polymer is a homopolymer.
 3. An articleaccording to claim 1 wherein the weight ratio of olefinic oxide polymerto cellulose is less than about 1:9.
 4. An article according to claim 1wherein the tube does not contain fiber reinforcement.
 5. An articleaccording to claim 1 wherein the tube contains fiber reinforcement. 6.An article according to claim 1 wherein the article is shirred.
 7. Anarticle according to claim 1 wherein the article contains no polyhydricalcohol softening agent.
 8. An article according to claim 1 wherein thearticle is a multilayer film.
 9. An article according to claim 2 whereinsaid homopolymer is poly(ethylene oxide).
 10. An article according toclaim 9 wherein said article contains no more than about 5 weight %polyhydric alcohol softening agent on a bone dry basis.
 11. An articleaccording to claim 9 wherein said poly(ethylene oxide) has an averagemolecular weight of about 100,000.
 12. An article according to claim 3wherein the weight ratio of olefinic oxide polymer to cellulose isbetween about 1:20 and 1:100.
 13. An article according to claim 8wherein the interior surface layer of the tube contains said olefinoxide polymer and at least one other layer is free of olefin oxidepolymer.
 14. A casing according to claim 1 wherein said casing containsless than 5% by weight of polyol.
 15. A casing according to claim 1wherein said casing has liquid smoke incorporated therein.
 16. A casingas defined in claim 1 wherein said casing tube wall thickness is between0.7 to 2.0 mils.
 17. A casing according to claim 1 wherein said casinghas a circumference of at least 4.4 cm.
 18. A casing according to claim1 wherein said casing has a circumference of at least 10.4 cm.
 19. Acasing according to claim 1 wherein said casing has a circumference ofbetween about 4.9 and 9.7 cm.
 20. A casing according to claim 1 whereinsaid casing has a circumference of between about 10.4 and 54.9 cm.
 21. Acasing according to claim 1 wherein said tubular casing comprises a tubehaving an interior surface coated with a transferable edible colorant.22. A casing according to claim 6 wherein said tubular casing comprisesa tube having an interior surface coated with a peeling aid compositionin an amount effective to promote peeling, wherein said peeling aidcomposition comprises a release agent and an anti-pleat lock agent. 23.A casing according to claim 22 wherein said peeling aid compositionfurther comprises a surfactant.
 24. A casing according to claim 22wherein said release agent comprises a salt of carboxymethylcellulose.25. A casing according to claim 22 wherein said peeling compositioncomprises a water soluble cellulose ether, a phospholipid and a polyol.26. A casing according to claim 22, wherein said release agent isselected from the group consisting of water-soluble cellulose or theirsalts, dextrin, casein, alginates, lecithin, chitosan, a phospholipid,or mixtures thereof.
 27. A casing according to claim 26, wherein saidanti-pleat lock agent comprises an oil or phospholipid.
 28. An article,as defined in claim 1, wherein said molecular weight is at least 90,000.29. An article, as defined in claim 1, wherein said molecular weight isbetween about 100,000 and 4,000,000.
 30. An article, as defined in claim1, wherein said molecular weight is between 90,000 and 200,000.
 31. Anarticle, as defined in claim 1, wherein said molecular weight is lessthan 1,000,000.
 32. A nonreinforced tubular cellulosic food casing inshirred form and without a polyhydric alcohol softening agent butcontaining poly(ethylene oxide) of greater than about 70,000 molecularweight and being uniformly dispersed through the tube wall in admixturewith the cellulose and in sufficient quantity so that the poly(ethyleneoxide)-to-cellulosic weight ratio is between about 0.5:95 and 5:95. 33.An article according to claim 32 wherein said article comprises a filmhaving a moisture content less than about 35% by weight bone dry gauge,and a film thickness less than 23 microns.
 34. An article according toclaim 32 wherein said article comprises a shirred film of at least 190feet.
 35. An article according to claim 32 wherein said articlecomprises a shirred film of at least 210 feet.
 36. An article accordingto claim 32 wherein said article comprises a shirred film of at least230 feet.